Level shifter circuit and method of operating the same

ABSTRACT

A circuit includes a level shifter circuit, an output circuit and a feedback circuit. The level shifter circuit is coupled to a first voltage supply, and is configured to receive at least an enable signal, a first input signal or a second input signal. The level shifter circuit is configured to generate at least a first signal responsive to at least the enable signal or the first input signal. The output circuit is coupled to at least the level shifter circuit and the first voltage supply, is configured to receive the first signal, and to generate at least an output signal or a set of feedback signals responsive to the first signal. The feedback circuit is coupled to the level shifter circuit, the output circuit and the first voltage supply, and is configured to receive the enable signal, an inverted enable signal and the set of feedback signals.

PRIORITY CLAIM

The present application is a continuation of U.S. application Ser. No.16/365,222, filed Mar. 26, 2019, which claims the benefit of U.S.Provisional Application No. 62/657,645, filed Apr. 13, 2018, thedisclosures of which are incorporated herein by reference in theirentireties.

BACKGROUND

The semiconductor integrated circuit (IC) industry has produced a widevariety of digital devices to address issues in a number of differentareas. Some of these digital devices, such as level shifter circuits,are configured to enable operation of circuits capable of operation indifferent voltage domains. As ICs have become smaller and more complex,operating voltages of these digital devices continue to decreaseaffecting IC performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. lA is a block diagram of an integrated circuit, in accordance withsome embodiments.

FIG. 1B is a block diagram of an integrated circuit, in accordance withsome embodiments.

FIG. 2 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 3 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 4 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 5 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 6 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 7 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 8 is a circuit diagram of a circuit, in accordance with someembodiments.

FIG. 9 is a circuit diagram of a circuit, in accordance with someembodiments.

FIGS. 10A-10B are a flowchart of a method of operating a circuit, suchas the circuit of FIGS. 1A-1B, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6,FIG. 7, FIG. 8 or FIG. 9, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides different embodiments, or examples,for implementing features of the provided subject matter. Specificexamples of components, materials, values, steps, arrangements, or thelike, are described below to simplify the present disclosure. These are,of course, merely examples and are not limiting. Other components,materials, values, steps, arrangements, or the like, are contemplated.For example, the formation of a first feature over or on a secondfeature in the description that follows may include embodiments in whichthe first and second features are formed in direct contact, and may alsoinclude embodiments in which additional features may be formed betweenthe first and second features, such that the first and second featuresmay not be in direct contact. In addition, the present disclosure mayrepeat reference numerals and/or letters in the various examples. Thisrepetition is for the purpose of simplicity and clarity and does not initself dictate a relationship between the various embodiments and/orconfigurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In accordance with some embodiments, a circuit includes a level shiftercircuit, a feedback circuit and an output circuit. The level shiftercircuit is configured to receive an enable signal and a first inputsignal having a first voltage swing. The level shifter circuit isfurther configured to generate a first signal and a second signalresponsive to at least the enable signal or the first input signal. Insome embodiments, the first signal or the second signal has a secondvoltage swing different from the first voltage swing.

In some embodiments, the feedback circuit is coupled to the levelshifter circuit, and configured to latch a previous state of the firstsignal responsive to at least the first signal or the second signal. Thefeedback circuit is controlled by a set of feedback signals. Thefeedback circuit includes a first path and a second path. In someembodiments, the first path and the second path are enabled or disabledby at least the set of feedback signals or the first enable signal.

The output circuit is coupled to the level shifter circuit and thefeedback circuit, and configured to generate an output signal based onat least the first signal. In some embodiments, the output circuit isconfigured to latch a previous state of the output signal responsive toat least the first signal or the second signal. In some embodiments, theoutput circuit is configured to generate at least the output signal orthe set of feedback signals responsive to the first signal.

In some embodiments, the level shifter includes a first path and asecond path. In some embodiments, the first path includes a firsttransistor, and the second path includes a second transistor. In someembodiments, by including the first transistor in the first path of thelevel shifter circuit, and by including the second transistor in thesecond path of the level shifter circuit, short circuit currents in thefirst path and the second path of the level shifter circuit areprevented when the level shifter circuit of the present disclosure isdisabled by the enable signal resulting in lower power consumption thanother approaches with short circuit currents.

Integrated Circuit

FIG. 1A is a block diagram of an integrated circuit 100A, in accordancewith some embodiments.

Integrated circuit 100A comprises an input circuit 102, an enablecircuit 104 a, an enable circuit 104 b, a level shifter circuit 110, afeedback circuit 120, a feedback circuit 130, and an output circuit 140.

Input circuit 102 is coupled to level shifter circuit 110. Input circuit102 is configured to receive an input signal IN, and to generate atleast an input signal INB. Input signal INB is inverted from inputsignal IN. In some embodiments, input circuit 102 is configured togenerate input signal INB and an input signal INBB (shown in FIG. 4).Input signal INBB is inverted from input signal INB. In someembodiments, input circuit 102 is configured to output one or more ofinput signal IN, input signal INB or input signal INBB to level shiftercircuit 110.

In some embodiments, input circuit 102 is coupled to a first voltagesupply node IN. In some embodiments, first voltage supply node IN has afirst supply voltage VDDI (FIGS. 2-9), and is therefore referred to asbeing in a VDDI voltage domain. In some embodiments, first supplyvoltage VDDI has a first voltage swing. In some embodiments, one or moreof input signal IN, input signal INB or input signal INBB have the firstvoltage swing.

Enable circuit 104 a is coupled to a first input terminal of levelshifter circuit 110 and an input terminal of feedback circuit 120.Enable circuit 104 a is configured to receive an enable signal EN, andto generate an inverted enable signal ENB. Inverted enable signal ENB isinverted from enable signal EN. In some embodiments, enable circuit 104a is configured to output at least enable signal EN or inverted enablesignal ENB to level shifter circuit 110. In some embodiments, enablecircuit 104 a is configured to output at least enable signal EN orinverted enable signal ENB to feedback circuit 120.

Enable circuit 104 b is coupled to a second input terminal of levelshifter circuit 110 and an input terminal of feedback circuit 130.Enable circuit 104 b is configured to receive enable signal EN, and togenerate inverted enable signal ENB. In some embodiments, enable circuit104 b is configured to output at least enable signal EN or invertedenable signal ENB to level shifter circuit 110. In some embodiments,enable circuit 104 b is configured to output at least enable signal ENor inverted enable signal ENB to feedback circuit 130. In someembodiments, enable circuit 104 b and enable circuit 104 a are part of asame enable circuit 204 (as shown in FIGS. 2-9). In some embodiments,enable circuit 104 b and enable circuit 104 a are different enablecircuits.

Level shifter circuit 110 is coupled to input circuit 102, enablecircuit 104 a, enable circuit 104 b and output circuit 140. In someembodiments, level shifter circuit 110 is further coupled to feedbackcircuit 120 and feedback circuit 130 (FIG. 1B). Level shifter circuit110 is configured to receive at least enable signal EN, input signal INor input signal INB. In some embodiments, level shifter circuit 110 isconfigured to receive at least enable signal EN, inverted enable signalENB, input signal IN, input signal INB or input signal INBB. In someembodiments, level shifter circuit 110 is configured to generate atleast a first signal SH1 or a second signal SH2 responsive to at leastenable signal EN, inverted enable signal ENB, input signal IN, inputsignal INB or input signal INBB. Level shifter circuit 110 is configuredto output at least first signal SH1 or second signal SH2 to outputcircuit 140. In other words, one or more of first signal SH1 or secondsignal SH2 is the output of level shifter circuit 110.

In some embodiments, level shifter circuit 110 is coupled to a secondvoltage supply node 2N having a second supply voltage VDDO (FIGS. 2-9),and is therefore referred to as being in a VDDO voltage domain. In someembodiments, second supply voltage VDDO is different from first supplyvoltage VDDI. In some embodiments, second supply voltage VDDO has asecond voltage swing different from the first voltage swing. In someembodiments, VDDO voltage domain is different from VDDI voltage domain.Level shifter circuit 110 is a level shifter circuit configured to shiftinput signals IN, INB, or INBB from the VDDI voltage domain that uses afirst supply voltage VDDI to the VDDO voltage domain that uses a secondsupply voltage VDDO.

In some embodiments, one or more of first signal SH1 or second signalSH2 are referred to as level shifted output signals. In someembodiments, one or more of first signal SH1 or second signal SH2 hasthe second voltage swing.

Output circuit 140 is coupled to level shifter circuit 110 and feedbackcircuits 120 and 130. An input terminal of output circuit 140 is coupledto at least an output terminal of level shifter circuit 110 or an outputterminal of corresponding feedback circuits 120 and 130, and configuredto receive at least first signal SH1 or second signal SH2. Outputcircuit 140 is configured to generate at least an output signal OUT orfeedback signals FS1, FS2 (collectively referred to as a “set offeedback signals FS”) responsive to at least first signal SH1 or secondsignal SH2.

A first output terminal of output circuit 140 is configured to outputthe output signal OUT. In some embodiments, a second output terminal ofoutput circuit 140 is configured to output the feedback signal FS1 tofeedback circuit 120, and a third output terminal of output circuit 140is configured to output the feedback signal FS2 to feedback circuit 130.Output signal OUT is the output signal of integrated circuit 100A or100B (FIG. 1B). Feedback signals FS1, FS2 are configured to controlcorresponding feedback circuits 120, 130.

In some embodiments, output signal OUT is referred to as a level shiftedoutput signal of integrated circuits 100A-100B. In some embodiments, oneor more of output signal OUT or set of feedback signals FS has thesecond voltage swing. In some embodiments, output signal OUT is a levelshifted version of input signal IN. In some embodiments, output circuit140 is configured to latch or maintain a previous state of the outputsignal OUT in response to at least enable signal EN or inverted enablesignal ENB. In some embodiments, output signal OUT is a latched orprevious state of the output signal OUT or a level shifted version ofinput signal IN.

Feedback circuit 120 is coupled to enable circuit 104 a and outputcircuit 140. In some embodiments, feedback circuit 120 is furthercoupled to level shifter circuit 110 (FIGS. 1B-9). Feedback circuit 120is configured to receive at least enable signal EN or inverted enablesignal ENB from enable circuit 104 a. Feedback circuit 120 is configuredto receive feedback signal FS1 from output circuit 140. In someembodiments, feedback circuit 120 is configured to output second signalSH2 to output circuit 140. In some embodiments, feedback circuit 120 isconfigured to adjust the second signal SH2 in response to at leastfeedback signal FS1, enable signal EN or inverted enable signal ENB. Insome embodiments, feedback circuit 120 is configured to latch ormaintain a previous state of the second signal SH2 in response to atleast feedback signal FS1, enable signal EN or inverted enable signalENB.

Feedback circuit 130 is coupled to enable circuit 104 b and outputcircuit 140. In some embodiments, feedback circuit 130 is furthercoupled to level shifter circuit 110 (FIGS. 1B-9). Feedback circuit 130is configured to receive at least enable signal EN or inverted enablesignal ENB from enable circuit 104 b. Feedback circuit 130 is configuredto receive feedback signal FS2 from output circuit 140. In someembodiments, feedback circuit 130 is configured to output first signalSH1 to output circuit 140. In some embodiments, feedback circuit 130 isconfigured to adjust the first signal SH1 in response to at leastfeedback signal FS2, enable signal EN or inverted enable signal ENB. Insome embodiments, feedback circuit 130 is configured to latch ormaintain a previous state of the first signal SH1 in response to atleast feedback signal FS2, enable signal EN or inverted enable signalENB. In some embodiments, at least feedback circuit 120, feedbackcircuit 130 or output circuit 140 is coupled to the second voltagesupply node 2N (FIGS. 2-9).

Integrated circuit 100A or 100B is configured to operate in a first modeor a second mode. For example, in the first mode, the output signal OUTcorresponds to a level shifted version of the input signal IN. In thesecond mode, the output signal OUT is a previous state or latched stateof the output signal OUT. In some embodiments, the first mode isreferred to as a level shifting mode, and the second mode is referred toas a latch mode. In some embodiments, integrated circuit 100A or 100B isreferred to as a level shifter with a memory element.

Level shifter circuit 110 and at least feedback circuit 120 or 130 arealso configured to operate in the first mode or the second mode in acomplementary manner

For example, in the first mode, level shifter circuit 110 is enabled,and feedback circuits 120 and 130 are disabled, and the output signalOUT corresponds to a level shifted version of the input signal IN.

Similarly, in the second mode, level shifter circuit 110 is disabled,and feedback circuits 120 and 130 are enabled, and the output circuit140 or feedback circuits 120 and 130 are configured to latch theprevious state of the output signal OUT. In the second mode, the outputsignal OUT is a previous state or latched state of the output signalOUT.

In some embodiments, level shifter circuit 110 is enabled or turned onby enable signal EN having a first logical value, and feedback circuits120 and 130 are disabled or turned off by enable signal EN having thefirst logical value.

In some embodiments, level shifter circuit 110 is disabled or turned offby enable signal EN having a second logical value, and feedback circuits120 and 130 are enabled or turned on by enable signal EN having thesecond logical value. In some embodiments, the second logical value isinverted from the first logical value.

In some embodiments, by disabling the level shifter circuit 110 andenabling the feedback circuits 120 and 130, integrated circuit 100A-100Bhas better power performance than other approaches. In some embodiments,by disabling the level shifter circuit 110 and enabling the feedbackcircuits 120 and 130, integrated circuit 100A-100B consumes less powerthan other approaches.

FIG. 1B is a block diagram of an integrated circuit 100B, in accordancewith some embodiments. Integrated circuit 100B is a variation ofintegrated circuit 100A, and similar detailed description is thereforeomitted. For example, integrated circuit 100B illustrates an example ofwhere the set of feedback signals FS are generated by the level shiftercircuit 110′.

Components that are the same or similar to those in one or more of FIGS.1A-1B and 2-9 (shown below) are given the same reference numbers, anddetailed description thereof is thus omitted.

In comparison with integrated circuit 100A of FIG. 1A, level shiftercircuit 110′ replaces level shifter circuit 110, feedback circuit 120′replaces feedback circuit 120, feedback circuit 130′ replaces feedbackcircuit 130 and output circuit 140′ replaces output circuit 140, andsimilar detailed description is therefore omitted.

In comparison with some embodiments of FIG. 1A, output circuit 140′ doesnot generate the set of feedback signals FS, and level shifter circuit110′ generates the set of feedback signals FS. Level shifter circuit110′ is coupled to input circuit 102, enable circuits 104 a and 104 b,feedback circuits 120′ and 130′ and output circuit 140′. Level shiftercircuit 110′ outputs feedback signal FS1 to feedback circuit 120′, andoutputs feedback signal FS2 to feedback circuit 130′. In someembodiments, first signal SH1 of FIG. 1B is a same signal as feedbacksignal FS1, and second signal SH2 of FIG. 1B is a same signal asfeedback signal FS2.

In some embodiments, feedback circuit 120′ is configured to maintain orset a state of the second signal SH2 in response to at least feedbacksignal FS1, first signal SH1, enable signal EN or inverted enable signalENB.

In some embodiments, feedback circuit 130′ is configured to maintain orset a state of the first signal SH1 in response to at least feedbacksignal FS2, second signal SH2, enable signal EN or inverted enablesignal ENB.

In comparison with some embodiments of FIG. 1A, output circuit 140′ doesnot latch the output signal OUT. In some embodiments, feedback circuits120′ and 130′ are configured to latch or maintain a previous state ofthe output signal OUT in response to at least the set of feedbacksignals FS, first signal SH1, second signal SH2, enable signal EN orinverted enable signal ENB.

FIG. 2 is a circuit diagram of a circuit 200, in accordance with someembodiments.

Circuit 200 is an embodiment of integrated circuit 100A of FIG. 1A.

Circuit 200 comprises an input circuit 202, an enable circuit 204, alevel shifter circuit 210, a feedback circuit 220, a feedback circuit230, and an output circuit 240.

Input circuit 202 is an embodiment of input circuit 102 of FIG. 1A, andsimilar detailed description is omitted. Input circuit 202 comprises aninverter 202 a coupled to a P-type Metal Oxide Semiconductor (PMOS)transistor mO. For ease of illustration, inverter 202 a and PMOStransistor m0 are not shown as being coupled to each other. Inverter 202a is coupled to the first voltage supply node IN. The first voltagesupply node IN is coupled to the PMOS transistor mO. Inverter 202 a andPMOS transistor m0 are configured to operate in the VDDI voltage domain.Inverter 202 a is configured to generate an input signal INB in responseto input signal IN. An input terminal (e.g., node n20) of inverter 202 ais configured to receive an input signal IN. An output terminal (e.g.,node n22) of inverter 202 a is configured to output input signal INB.Input circuit 202 and inverter 202 a are coupled to level shiftercircuit 210. For ease of illustration, input circuit 202 and inverter202 a are not shown as being coupled to level shifter circuit 210.

PMOS transistor m0 is configured to provide a supply voltage VDDI to thefirst voltage supply node IN and inverter 202 a. PMOS transistor m0 isconfigured to receive a power enable signal Pin. A gate terminal of PMOStransistor m0 is configured to receive the power enable signal Pin. PMOStransistor m0 is turned on or off based on the power enable signal Pin.A drain terminal of PMOS transistor m0 is configured to receive thesupply voltage VDDI from a node (not labelled). A source terminal ofPMOS transistor m0 is coupled with the first voltage supply node IN andinverter 202 a. In some embodiments, turning on the input power tocircuit 200 comprises turning on PMOS transistor m0 responsive to powerenable signal Pin, such that PMOS transistor m0 provides supply voltageVDDI to the first voltage supply node IN and inverter 202 a. In someembodiments, turning off the input power to circuit 200 comprisesturning off PMOS transistor m0 responsive to power enable signal Pin,such that PMOS transistor m0 does not provide supply voltage VDDI to thefirst voltage supply node IN and inverter 202 a. Other transistor typesin input circuit 202 are within the scope of the present disclosure.

Enable circuit 204 is an embodiment of at least enable circuit 104 a or104 b of FIG. 1A, and similar detailed description is omitted. Enablecircuit 204 comprises an inverter 204 a coupled to the second voltagesupply node 2N. Enable circuit 204 and inverter 204 a are coupled tolevel shifter circuit 210, feedback circuit 220, feedback circuit 230and output circuit 240. For ease of illustration, enable circuit 204 andinverter 204 a are not shown as being coupled to level shifter circuit210, feedback circuit 220, feedback circuit 230 and output circuit 240.

Inverter 204 a is configured to operate in the VDDO voltage domain.Inverter 204 a is configured to generate inverted enable signal ENB inresponse to enable signal EN. An input terminal n30 of inverter 204 a isconfigured to receive enable signal EN. In some embodiments, inputterminal n30 of inverter 204 a is coupled to level shifter circuit 210,feedback circuit 220, feedback circuit 230 and output circuit 240. Anoutput terminal n32 of inverter 204 a is configured to output invertedenable signal ENB to feedback circuits 220 and 230 and output circuit240. Output terminal n32 of inverter 204 a is coupled to feedbackcircuits 220 and 230 and output circuit 240.

Level shifter circuit 210 is an embodiment of level shifter circuit 110of FIG. 1A, and similar detailed description is omitted. Level shiftercircuit 210 is configured to shift input signals IN or INB from the VDDIvoltage domain to the VDDO voltage domain. Level shifter circuit 210 iscoupled to at least input circuit 202, enable circuit 204, feedbackcircuit 220, feedback circuit 230, and output circuit 240. Level shifter210 is configured to receive at least enable signal EN, input signal INor input signal INB. Level shifter 210 is configured to generate firstsignal SH1 responsive to at least enable signal EN or input signal IN.Level shifter 210 is configured to generate second signal SH2 responsiveto at least enable signal EN or input signal INB. First signal SH1 orsecond signal SH2 is the output of level shifter circuit 210. Levelshifter circuit 210 is configured to operate in the VDDO voltage domain.In some embodiments, one or more of first signal SH1 or second signalSH2 is the level shifted output signal (e.g., second voltage swing) ofinput signal IN (e.g., first voltage swing).

Level shifter circuit 210 comprises P-type Metal Oxide Semiconductor(PMOS) transistors m1, m2, m3 and m4 and N-type Metal OxideSemiconductor (NMOS) transistors m5, m6, m7 and m8. Each of PMOStransistors m1, m2, m3, and m4 and NMOS transistors m5, m6, m7 and m8 isconfigured to operate in the VDDO voltage domain.

PMOS transistors m1 and m3 (collectively referred to as “a first set oftransistors”) are coupled between a first node n3 of level shiftercircuit 210 and the second voltage supply node 2N. A voltage of thefirst node n3 corresponds to a voltage of second signal SH2.

PMOS transistors m2 and m4 (collectively referred to as “a second set oftransistors”) are coupled between a second node n4 of level shiftercircuit 210 and the second voltage supply node 2N. A voltage of thesecond node n4 corresponds to a voltage of first signal SH1.

A gate terminal of PMOS transistor m1 is coupled to at least the secondnode n4 and configured to receive the first signal SH1. PMOS transistorm1 is turned on or off based on first signal SH1. A source terminal ofPMOS transistor m1 is coupled with second voltage supply node 2N.

A gate terminal of PMOS transistor m2 is coupled to at least the firstnode n3 and configured to receive the second signal SH2. PMOS transistorm2 is turned on or off based on second signal SH2. A source terminal ofPMOS transistor m2 is coupled with second voltage supply node 2N.

A gate terminal of PMOS transistor m3 is coupled to at least node n22and configured to receive the input signal INB. PMOS transistor m3 isturned on or off based on input signal INB. A drain terminal of PMOStransistor m3 is coupled with at least the first node n3. A drainterminal of PMOS transistor m1 and a source terminal of PMOS transistorm3 are coupled to each other at a node nl.

A gate terminal of PMOS transistor m4 is coupled to at least node n20and configured to receive the input signal IN. PMOS transistor m4 isturned on or off based on input signal IN. A drain terminal of PMOStransistor m4 is coupled with at least the second node n4. A drainterminal of PMOS transistor m2 and a source terminal of PMOS transistorm4 are coupled to each other at a node n2.

NMOS transistor m7 (collectively referred to as “a third set oftransistors”) and NMOS transistor m8 (collectively referred to as “afourth set of transistors”) are each coupled to a reference supply nodeVSS.

A gate terminal of NMOS transistor m7 is coupled to at least node n22and configured to receive input signal INB. NMOS transistor m7 is turnedon or off based on input signal INB. A source terminal of NMOStransistor m7 is coupled with at least the reference supply node VSS.

A gate terminal of NMOS transistor m8 is coupled to at least node n20and configured to receive input signal IN. NMOS transistor m8 is turnedon or off based on input signal IN. A source terminal of NMOS transistorm8 is coupled with at least the reference supply node VSS.

NMOS transistor m5 (collectively referred to as “a fifth set oftransistors”) is coupled between NMOS transistor m7 and the first noden3.

A gate terminal of NMOS transistor m5 is coupled to at least node n30and configured to receive enable signal EN. NMOS transistor m5 is turnedon or off based on enable signal EN. A drain terminal of NMOS transistorm5 and the drain terminal of PMOS transistor m3 are coupled to eachother at first node n3. A source terminal of NMOS transistor m5 and adrain terminal of NMOS transistor m7 are coupled to each other.

NMOS transistor m6 (collectively referred to as “a sixth set oftransistors”) is coupled between NMOS transistor m8 and the second noden4.

A gate terminal of NMOS transistor m6 is coupled to at least node n30and configured to receive enable signal EN. NMOS transistor m6 is turnedon or off based on enable signal EN. A drain terminal of NMOS transistorm6 and the drain terminal of PMOS transistor m4 are coupled to eachother at second node n4. A source terminal of NMOS transistor m6 and adrain terminal of NMOS transistor m8 are coupled to each other.

NMOS transistor m5, NMOS transistor m7, PMOS transistor m1 and PMOStransistor m3 are referred to as a first input path of level shiftercircuit 210. NMOS transistor m6, NMOS transistor m8, PMOS transistor m2and PMOS transistor m4 are referred to as a second input path of levelshifter circuit 210. The first input path and the second input path oflevel shifter circuit 210 are enabled or disabled by enable signal EN.

Feedback circuit 220 is an embodiment of feedback circuit 120 of FIG.1A, and similar detailed description is omitted. Feedback circuit 220 isconfigured to receive enable signal EN, inverted enable signal ENB andfeedback signal FS1. Feedback circuit 220 is coupled to at least thesecond voltage supply node 2N or the second first node n3 of levelshifter circuit 210. Feedback circuit 220 comprises PMOS transistors m9and m11 and NMOS transistors m13 and m15. Each of PMOS transistors m9and m11 and NMOS transistors m13 and m15 is configured to operate in theVDDO voltage domain.

A gate terminal of PMOS transistor m9 is coupled to at least a node n6of output circuit 240 and configured to receive the feedback signal FS1.PMOS transistor m9 is turned on or off based on feedback signal FS1. Asource terminal of PMOS transistor m9 is coupled with second voltagesupply node 2N. A drain terminal of PMOS transistor m9 is coupled with asource terminal of PMOS transistor m11.

A gate terminal of PMOS transistor m11 is coupled to at least node n30and configured to receive enable signal EN. PMOS transistor m11 isturned on or off based on enable signal EN. A drain terminal of PMOStransistor m11 is coupled with at least the first node n3.

A gate terminal of NMOS transistor m13 is coupled to at least node n32and configured to receive inverted enable signal ENB. NMOS transistorm13 is turned on or off based on inverted enable signal ENB. A drainterminal of NMOS transistor m13 and the drain terminal of PMOStransistor m11 are coupled to each other at first node n3. A sourceterminal of NMOS transistor m13 and a drain terminal of NMOS transistorm15 are coupled to each other.

A gate terminal of NMOS transistor m15 is coupled to at least node n6 ofoutput circuit 240 and configured to receive feedback signal FS1. Insome embodiments, each of the gate terminal of NMOS transistor m15, noden6 of output circuit 240 and the gate terminal of PMOS transistor m9 arecoupled together. NMOS transistor m15 is turned on or off based onfeedback signal FS1. A source terminal of NMOS transistor m15 is coupledwith at least the reference supply node VSS.

Each of the drain terminal of NMOS transistor m13, the drain terminal ofPMOS transistor m11, the drain terminal of NMOS transistor m5, the drainterminal of PMOS transistor m3 and the gate terminal of PMOS transistorm2 are coupled to each other at first node n3.

NMOS transistor m13, NMOS transistor m15, PMOS transistor m9 and PMOStransistor m11 are referred to as a first feedback path of feedbackcircuit 220.

Feedback circuit 220 or level shifter circuit 210 is configured to setthe voltage of first node n3 which corresponds to second signal SH2.NMOS transistors m13 and m15 and PMOS transistors m9 and m11 of feedbackcircuit 220 or NMOS transistors m5 and m7 and PMOS transistors m1 and m3of level shifter circuit 210 are configured to set the voltage of firstnode n3.

For example, in some embodiments, if NMOS transistors m5 and m7 areturned on, transistors m5 and m7 are configured to pull first node n3towards reference voltage VSS. Similarly, in some embodiments, if NMOStransistors m13 and m15 are turned on, transistors m13 and m15 areconfigured to pull first node n3 towards reference voltage VS S. Forexample, in some embodiments, if PMOS transistors m1 and m3 are turnedon, PMOS transistors m1 and m3 are configured to pull first node n3towards supply voltage VDDO. Similarly, in some embodiments, if PMOStransistors m9 and m11 are turned on, PMOS transistors m9 and m11 areconfigured to pull first node n3 towards supply voltage VDDO.

Feedback circuit 230 is an embodiment of feedback circuit 130 of FIG.1A, and similar detailed description is omitted. Feedback circuit 230 isconfigured to receive enable signal EN, inverted enable signal ENB andfeedback signal FS2. Feedback circuit 230 is coupled to at least thesecond voltage supply node 2N or the second node n4 of level shiftercircuit 210. Feedback circuit 230 comprises PMOS transistors m10 and m12and NMOS transistors m14 and m16. Each of PMOS transistors m10 and m12and NMOS transistors m14 and m16 is configured to operate in the VDDOvoltage domain.

A gate terminal of PMOS transistor m10 is coupled to at least a node n7of output circuit 240 and configured to receive the feedback signal FS2.PMOS transistor m10 is turned on or off based on feedback signal FS2. Asource terminal of PMOS transistor m10 is coupled with second voltagesupply node 2N. A drain terminal of PMOS transistor m10 is coupled witha source terminal of PMOS transistor m12.

A gate terminal of PMOS transistor m12 is coupled to at least node n30and configured to receive enable signal EN. PMOS transistor m12 isturned on or off based on enable signal EN. A drain terminal of PMOStransistor m12 is coupled with at least the second node n4.

A gate terminal of NMOS transistor m14 is coupled to at least node n32and configured to receive inverted enable signal ENB. NMOS transistorm14 is turned on or off based on inverted enable signal ENB. A drainterminal of NMOS transistor m14 and the drain terminal of PMOStransistor m12 are coupled to each other at second node n4. A sourceterminal of NMOS transistor m14 and a drain terminal of NMOS transistorm16 are coupled to each other.

A gate terminal of NMOS transistor m16 is coupled to at least node n7 ofoutput circuit 240 and configured to receive feedback signal FS2. Insome embodiments, each of the gate terminal of NMOS transistor m16, noden7 of output circuit 240 and the gate terminal of PMOS transistor m10are coupled together. NMOS transistor m16 is turned on or off based onfeedback signal FS2. A source terminal of NMOS transistor m16 is coupledwith at least the reference supply node VSS.

NMOS transistor m14, NMOS transistor m16, PMOS transistor m10 and PMOStransistor m12 are referred to as a second feedback path of feedbackcircuit 230. The first feedback path of feedback circuit 220 and thesecond feedback path of feedback circuit 230 are enabled or disabled byat least enable signal EN.

Feedback circuit 230 or level shifter circuit 210 is configured to setthe voltage of second node n4 which corresponds to first signal SH1.NMOS transistors m14 and m16 and PMOS transistors m10 and m12 offeedback circuit 230 or NMOS transistors m6 and m8 and PMOS transistorsm2 and m4 of level shifter circuit 210 are configured to set the voltageof second node n4.

For example, in some embodiments, if NMOS transistors m6 and m8 areturned on, transistors m6 and m8 are configured to pull second node n4towards reference voltage VSS. Similarly, in some embodiments, if NMOStransistors m14 and m16 are turned on, transistors m14 and m16 areconfigured to pull second node n4 towards reference voltage VSS. Forexample, in some embodiments, if PMOS transistors m2 and m4 are turnedon, PMOS transistors m2 and m4 are configured to pull second node n4towards supply voltage VDDO. Similarly, in some embodiments, if PMOStransistors m10 and m12 are turned on, PMOS transistors m10 and m12 areconfigured to pull second node n4 towards supply voltage VDDO.

Level shifter circuit 210 and feedback circuits 220 and 230 operate in acomplementary manner For example, in some embodiments, if the levelshifter circuit 210 is enabled, then feedback circuits 220 and 230 aredisabled, and vice versa. For example, in some embodiments, if the levelshifter circuit 210 is disabled, then feedback circuits 220 and 230 areenabled, and vice versa.

For example, in some embodiments, if level shifter circuit 210 isenabled, then NMOS transistor m5 of the first input path of levelshifter circuit 210 and NMOS transistor m6 of the second input path oflevel shifter circuit 210 will be enabled or turned on by enable signalEN. Similarly, if feedback circuit 220 and feedback circuit 230 aredisabled, then NMOS transistor m13 of the first feedback path offeedback circuit 220 and NMOS transistor m14 of the second feedback pathof feedback circuit 230 will be disabled or turned off by invertedenable signal ENB, and PMOS transistor m11 of the first feedback path offeedback circuit 220 and PMOS transistor m12 of the second feedback pathof feedback circuit 230 will be disabled or turned off by enable signalEN.

For example, in some embodiments, if the level shifter circuit 200 isdisabled, then NMOS transistor m5 of the first input path of levelshifter circuit 210 and NMOS transistor m6 of the second input path oflevel shifter circuit 210 will be disabled or turned off by enablesignal EN. Similarly, if feedback circuit 220 and feedback circuit 230are enabled, then NMOS transistor m13 of the first feedback path offeedback circuit 220 and NMOS transistor m14 of the second feedback pathof feedback circuit 230 will be enabled or turned on by inverted enablesignal ENB, and PMOS transistor mll of the first feedback path offeedback circuit 220 and PMOS transistor m12 of the second feedback pathof feedback circuit 230 will be enabled or turned on by enable signalEN.

In some embodiments, if EN has a high logical value (e.g. “1”), thenlevel shifter circuit 210 and NMOS transistors m5 and m6 are enabled,NMOS transistor m13 and PMOS transistor ml 1 of feedback circuit 220 aredisabled, and NMOS transistor m14 and PMOS transistor m12 of feedbackcircuit 230 are disabled. In these embodiments, if level shifter circuit210 is enabled or feedback circuits 220 and 230 are disabled, then levelshifter circuit 210 will output a level shifted version (e.g., firstsignal SH1 or second signal SH2) of input signal IN, and the outputsignal OUT of output circuit 240 will correspond to the level shiftedversion (e.g., first signal SH1 or second signal SH2) of input signalIN.

In some embodiments, if EN has a low logical value (e.g. “0”), thenlevel shifter circuit 210 and NMOS transistors m5 and m6 are disabled,NMOS transistor m13 and PMOS transistor ml 1 of feedback circuit 220 areenabled, and NMOS transistor m14 and PMOS transistor m12 of feedbackcircuit 230 are enabled. In these embodiments, if level shifter circuit210 is disabled or feedback circuits 220 and 230 are enabled, then theoutput circuit 240 will output an output signal OUT that corresponds toa previous or latched state of output signal OUT.

Other values for enable signal EN, inverted enable signal ENB,transistors types or configurations in level shifter circuit 210,feedback circuit 220, and feedback circuit 230 are within the scope ofthe present disclosure.

Output circuit 240 is an embodiment of output circuit 140 of FIG. 1A,and similar detailed description is omitted. Output circuit 240 isconfigured to receive at least enable signal EN, inverted enable signalENB or first signal SH1. Output circuit 240 is configured to generate atleast output signal OUT or the set of feedback signals FS responsive toat least first signal SH1, enable signal EN or inverted enable signalENB. Output circuit 240 is coupled to at least the second voltage supplynode 2N, the second node n4 of level shifter circuit 210, feedbackcircuit 220 or feedback circuit 230. Output circuit 240 is configured tooutput feedback signal FS1 to feedback circuit 220, and to outputfeedback signal FS2 to output circuit 230.

Output circuit 240 comprises PMOS transistors m20 and m21, NMOStransistors m22 and m23, an inverter 242, an inverter 244, an inverter246, an inverter 248, an inverter 250 and a transmission gate 252. Eachof PMOS transistors m20 and m21, NMOS transistors m22 and m23, inverters242, 244, 246, 248 and 250 and transmission gate 252 is configured tooperate in the VDDO voltage domain.

PMOS transistors m20 and m21 and NMOS transistors m22 and m23 arecoupled to level shifter circuit 210 and feedback circuit 230 by thesecond node n4. PMOS transistors m20 and m21 and NMOS transistors m22and m23 are configured to generate output signal OUT in response to atleast first signal SH1, enable signal EN or inverted enable signal ENB.

In some embodiments, if enable signal EN is logically high, then PMOStransistors m20 and m21 and NMOS transistors m22 and m23 are configuredas an inverter.

A gate terminal of PMOS transistor m20 is coupled to at least a gateterminal of NMOS transistor m23 or the second node n4 of level shiftercircuit 210. The gate terminal of PMOS transistor m20 and the gateterminal of NMOS transistor m23 are configured to receive the firstsignal SH1. PMOS transistor m20 is turned on or off based on firstsignal SH1. A source terminal of PMOS transistor m20 is coupled withsecond voltage supply node 2N. A drain terminal of PMOS transistor m20is coupled with a source terminal of PMOS transistor m21.

A gate terminal of PMOS transistor m21 is coupled to at least node n32and configured to receive inverted enable signal ENB. PMOS transistorm21 is turned on or off based on inverted enable signal ENB. Each of adrain terminal of PMOS transistor m21, a drain terminal of NMOStransistor m22, an input terminal of inverter 242, an input terminal ofinverter 248, an output terminal of transmission gate 252 and a node n5are coupled to each other.

A gate terminal of NMOS transistor m22 is coupled to at least node n30and configured to receive enable signal EN. NMOS transistor m22 isturned on or off based on enable signal EN. A source terminal of NMOStransistor m22 and a drain terminal of NMOS transistor m23 are coupledto each other.

The gate terminal of NMOS transistor m23 is coupled to at least the gateterminal of PMOS transistor m20 or the second node n4 of level shiftercircuit 210. The gate terminal of NMOS transistor m23 is configured toreceive first signal SH1. NMOS transistor m23 is turned on or off basedon first signal SH1. A source terminal of NMOS transistor m23 is coupledwith at least the reference supply node VSS.

Each of the drain terminal of NMOS transistor m14, the drain terminal ofPMOS transistor m12, the drain terminal of NMOS transistor m6, the drainterminal of PMOS transistor m4, the gate terminal of PMOS transistor ml,the gate terminal of PMOS transistor m20 and the gate terminal of NMOStransistor m23 are coupled to each other at second node n4.

Inverter 242 is coupled between node n5 and a node n8. Inverter 242 isconfigured to generate an inverted output signal OUTB in response tooutput signal OUT. An input terminal of inverter 242 is coupled to atleast the drain terminal of PMOS transistor m21, the drain terminal ofNMOS transistor m22, the output terminal of transmission gate 252 ornode n5. The input terminal of inverter 242 is configured to receive theoutput signal OUT from at least node n5. An output terminal of inverter242 is coupled to at least node n8, an input terminal of inverter 244 oran input terminal of inverter 246. The output terminal of inverter 242is configured to output the inverted output signal OUTB to at least noden8, the input terminal of inverter 244 or the input terminal of inverter246.

Inverter 244 is coupled between node n8 and an output node of circuit200. Inverter 244 is configured to generate output signal OUT inresponse to the inverted output signal OUTB. The input terminal ofinverter 244 is coupled to at least node n8, the output terminal ofinverter 242 or the input terminal of inverter 246. The input terminalof inverter 244 is configured to receive the inverted output signal OUTBfrom inverter 242. An output terminal of inverter 244 is coupled to theoutput node of circuit 200. The output terminal of inverter 244 isconfigured to output the output signal OUT to the output node of circuit200.

Inverter 246 is coupled between node n8 and transmission gate 252.Inverter 246 is configured to generate output signal OUT in response tothe inverted output signal OUTB. The input terminal of inverter 246 iscoupled to at least node n8, the output terminal of inverter 242 or theinput terminal of inverter 244. The input terminal of inverter 242 isconfigured to receive the inverted output signal OUTB from at least noden8. An output terminal of inverter 246 is coupled to an input terminalof transmission gate 252. The output terminal of inverter 246 isconfigured to output the output signal OUT to the input terminal oftransmission gate 252.

Inverter 248 is coupled between node n5 and node n6. Inverter 248 isconfigured to generate feedback signal FS1 in response to output signalOUT. In some embodiments, feedback signal FS1 corresponds to theinverted output signal OUTB. An input terminal of inverter 248 iscoupled to at least the drain terminal of PMOS transistor m21, the drainterminal of NMOS transistor m22, the output terminal of transmissiongate 252, node n5 or the input terminal of inverter 242. The inputterminal of inverter 248 is configured to receive the output signal OUTfrom at least node n5. An output terminal of inverter 248 is coupled toat least node n6, an input terminal of inverter 250, the gate terminalof PMOS transistor m9 or the gate terminal of NMOS transistor m15. Theoutput terminal of inverter 248 is configured to output feedback signalFS1 to at least node n6, input terminal of inverter 250, the gateterminal of PMOS transistor m9 or the gate terminal of NMOS transistorm15.

Inverter 250 is coupled between node n6 and node n7. Inverter 250 isconfigured to generate feedback signal FS2 in response to feedbacksignal FS1. In some embodiments, feedback signal FS2 corresponds tooutput signal OUT. An input terminal of inverter 250 is coupled to atleast the output terminal of inverter 248, node n6, the gate terminal ofPMOS transistor m9 or the gate terminal of NMOS transistor m15. Theinput terminal of inverter 250 is configured to receive feedback signalFS1 from inverter 248 by node n6. An output terminal of inverter 250 iscoupled to at least node n7, the gate terminal of PMOS transistor m10 orthe gate terminal of NMOS transistor m16. The output terminal ofinverter 250 is configured to output feedback signal FS2 to at leastnode n7, the gate terminal of PMOS transistor m10 or the gate terminalof NMOS transistor m16.

Transmission gate 252 is coupled between the output terminal of inverter246 and node n5. Transmission gate 252 has a first input terminalconfigured to receive enable signal EN, a second input terminalconfigured to receive inverted enable signal ENB and a third inputterminal configured to receive output signal OUT. Transmission gate 252has an output terminal configured to output enable signal EN.

Transmission gate 252 comprises a PMOS transistor m24 and an NMOStransistor m25. A gate terminal of PMOS transistor m24 is coupled to atleast node n30 and configured to receive enable signal EN. A gateterminal of NMOS transistor m25 is coupled to at least node n32 andconfigured to receive inverted enable signal ENB. PMOS transistor m24 isturned on or off based on enable signal EN. NMOS transistor m25 isturned on or off based on inverted enable signal ENB. One of a drain ora source terminal of PMOS transistor m24 is coupled to one of a drain ora source terminal of NMOS transistor m25, and is configured as the thirdinput terminal of transmission gate 252. The other of the source or thedrain source terminal of PMOS transistor m24 is coupled to the other ofthe source or the drain terminal of NMOS transistor m25, and isconfigured as the output terminal of transmission gate 252.

Transmission gate 252 is enabled (e.g., turned on) or disabled (e.g.,turned off) in response to enable signal EN and inverted enable signalENB. If enabled, transmission gate 252 is configured to output or passthe output signal OUT to at least node n5. If disabled, transmissiongate 252 does not pass or output the output signal OUT to node n5.

In some embodiments, inverter 242, inverter 246 and transmission gate252 are configured as a latch circuit (not labelled) configured to latcha previous state of the output signal OUT responsive to at least enablesignal EN or the inverted enable signal.

In some embodiments, if level shifter circuit 210 is disabled by enablesignal EN or feedback circuits 220 and 230 are enabled by enable signalEN, then the latch circuit (e.g., inverter 242, inverter 246 andtransmission gate 252) is enabled by at least enable signal EN orinverted enable signal ENB, and the output signal OUT is a latched or aprevious state of the output signal OUT.

In some embodiments, if level shifter circuit 210 is enabled by enablesignal EN or feedback circuits 220 and 230 are disabled by enable signalEN, then the output signal OUT is a level shifted version of inputsignal IN. In these embodiments, the output signal OUT is also invertedfrom the first signal SH1.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 210, and by including NMOS transistor m6 in thesecond path of level shifter circuit 210, short circuit currents in thefirst path and the second path of level shifter circuit 210 areprevented when level shifter circuit 210 is disabled by the enablesignal EN resulting in lower power consumption than other approaches.

FIG. 3 is a circuit diagram of a circuit 300, in accordance with someembodiments. Circuit 300 is an embodiment of integrated circuit 100A ofFIG. 1A, and similar detailed description is therefore omitted.

Circuit 300 is a variation of circuit 200 of FIG. 2, and similardetailed description is therefore omitted. In comparison with circuit200 of FIG. 2, feedback signal FS2 of circuit 300 corresponds to thesignal at node n5, and feedback signal FS1 of circuit 300 corresponds tothe signal at node n8. In other words, control of feedback circuit 320is changed by connecting feedback circuit 320 to node n8, and control offeedback circuit 330 is changed by connecting feedback circuit 330 tonode n5.

In comparison with circuit 200 of FIG. 2, feedback circuit 320 replacesfeedback circuit 220, feedback circuit 330 replaces feedback circuit 230and output circuit 340 replaces output circuit 240, and similar detaileddescription is therefore omitted.

In comparison with output circuit 240 of FIG. 2, output circuit 340 doesnot include inverter 248, inverter 250, and nodes n6 and n7, andtherefore feedback signal FS1 of circuit 300 is not generated byinverter 248, and feedback signal FS2 of circuit 300 is not generated byinverter 250.

In comparison with feedback circuit 220 of FIG. 2, the gate terminal ofPMOS transistor m9 of feedback circuit 320 and the gate terminal of NMOStransistor m15 of feedback circuit 320 are coupled to node n8. Feedbacksignal FS1 corresponds to the signal at node n8.

Node n8 of output circuit 340 is coupled to at least the output terminalof inverter 242, the input terminal of inverter 244, the input terminalof inverter 246, the gate terminal of PMOS transistor m9 or the gateterminal of NMOS transistor m15. Inverter 242 of output circuit 340 isconfigured to generate feedback signal FS1 in response to feedbacksignal FS2 or output signal OUT. Thus, inverter 242 is configured tocontrol feedback circuit 320 by feedback signal FS1.

In comparison with feedback circuit 230 of FIG. 2, the gate terminal ofPMOS transistor m10 of feedback circuit 330 and the gate terminal ofNMOS transistor m16 of feedback circuit 330 are coupled to node n5.

Node n5 of output circuit 340 is coupled to at least the drain terminalof PMOS transistor m21, the drain terminal of NMOS transistor m22, theoutput terminal of transmission gate 252, the input terminal of inverter242, the gate terminal of PMOS transistor m10 or the gate terminal ofNMOS transistor m16. Feedback signal FS2 corresponds to the signal atnode n5.

Feedback signal FS2 of circuit 300 is generated by transmission gate 252or by PMOS transistors m20 and m21 and NMOS transistors m22 and m23.Feedback circuit 330 is configured to be controlled by transmission gate252 of output circuit 340 or controlled by PMOS transistors m20 and m21and NMOS transistors m22 and m23 of output circuit 340. Feedback circuit330 is controlled by feedback signal FS2.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 210, and by including NMOS transistor m6 in thesecond path of level shifter circuit 210, short circuit currents in thefirst path and the second path of level shifter circuit 210 areprevented when level shifter circuit 210 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 340 such thatfeedback circuit 320 is coupled to node n8 or feedback circuit 330 iscoupled to node n5, circuit 300 includes less circuit elements thanother approaches resulting in less lower power consumption and less areathan other approaches.

FIG. 4 is a circuit diagram of a circuit 400, in accordance with someembodiments. Circuit 400 is an embodiment of integrated circuit 100A ofFIG. 1A, and similar detailed description is therefore omitted.

Circuit 400 is a variation of circuit 200 of FIG. 2, and similardetailed description is therefore omitted. In comparison with circuit200 of FIG. 2, feedback circuit 420 and feedback circuit 430 areconfigured to assist with latching the output signal OUT. Furthermore,in comparison with circuit 200 of FIG. 2, feedback signal FS2 of circuit400 corresponds to the signal at node n5, and feedback signal FS1 ofcircuit 400 corresponds to the signal at node n6. In other words,control of feedback circuit 420 is changed by connecting feedbackcircuit 420 to node n6, and control of feedback circuit 430 is changedby connecting feedback circuit 430 to node n5. Furthermore, incomparison with circuit 200 of FIG. 2, feedback circuit 420 and feedbackcircuit 430 are configured to latch output signal OUT.

In comparison with circuit 200 of FIG. 2, input circuit 402 replacesinput circuit 202, level shifter circuit 410 replaces level shiftercircuit 210, feedback circuit 420 replaces feedback circuit 220,feedback circuit 430 replaces feedback circuit 230 and output circuit440 replaces output circuit 240, and similar detailed description istherefore omitted.

Input circuit 402 is an embodiment of input circuit 202 of FIGS. 1A-1B,and similar detailed description is omitted.

Input circuit 402 is a variation of input circuit 202 of FIG. 2. Inputcircuit 402 comprises inverter 202 a, an inverter 402 a and PMOStransistor mO. Inverter 402 a is coupled to each of inverter 202 a andPMOS transistor mO. For ease of illustration, inverter 202 a, inverter402 a and PMOS transistor m0 are not shown as being coupled to eachother. An output terminal (e.g., node n22) of inverter 202 a is coupledto an input terminal of inverter 402 a. Inverter 402 a is coupled toPMOS transistor m0 by the first voltage supply node IN. Inverter 402 ais configured to operate in the VDDI voltage domain. Inverter 402 a isconfigured to generate an input signal INBB in response to input signalINB. An input terminal of inverter 402 a is configured to receive inputsignal INB. An output terminal (e.g., node n24) of inverter 402 a isconfigured to output input signal INBB. Input circuit 402, inverter 202a and inverter 402 a are coupled to level shifter circuit 410. For easeof illustration, input circuit 402, inverter 202 a and inverter 402 aare not shown as being coupled to level shifter circuit 410. PMOStransistor m0 is configured to provide supply voltage VDDI to the firstvoltage supply node IN, inverter 202 a and inverter 402 a. In comparisonwith input circuit 200 of FIG. 2, the source terminal of PMOS transistorm0 is coupled with the first voltage supply node IN, inverter 202 a andinverter 402 a. In some embodiments, turning on the input power tocircuit 400 comprises turning on PMOS transistor m0 responsive to powerenable signal Pin, such that PMOS transistor m0 provides supply voltageVDDI to the first voltage supply node IN, inverter 202 a and inverter402 a. In some embodiments, turning off the input power to circuit 400comprises turning off PMOS transistor m0 responsive to power enablesignal Pin, such that PMOS transistor m0 does not provide supply voltageVDDI to the first voltage supply node IN, inverter 202 a and inverter402 a. Other transistor types in input circuit 402 are within the scopeof the present disclosure.

In comparison with level shifter circuit 210 of FIG. 2, the gateterminal of PMOS transistor m3 of level shifter circuit 410 and the gateterminal of NMOS transistor m7 of level shifter circuit 410 are coupledto node n22 of input circuit 402, and configured to receive input signalINB. In comparison with level shifter circuit 210 of FIG. 2, the gateterminal of PMOS transistor m4 of level shifter circuit 410 and the gateterminal of NMOS transistor m8 of level shifter circuit 410 are coupledto node n24 of input circuit 402, and configured to receive input signalINBB.

In comparison with output circuit 240 of FIG. 2, output circuit 440includes an inverter 442, an inverter 448 and an inverter 450. Outputcircuit 440 and inverters 442, 448 and 450 are configured to operate inthe VDDO voltage domain.

Inverter 442 is coupled between the second node n4 of level shiftercircuit 410 and node n5 of circuit 400. Inverter 442 is configured togenerate the output signal OUT (e.g., the feedback signal FS2) inresponse to the first signal SH1. In some embodiments, the output signalOUT corresponds to feedback signal FS2. The input terminal of inverter442 is coupled to at least the second node n4 of level shifter circuit410. The input terminal of inverter 442 is configured to receive thefirst signal SH1 from level shifter circuit 410. An output terminal ofinverter 442 is coupled to at least an input terminal of inverter 448 orn5 node of circuit 400. The output terminal of inverter 442 isconfigured to output the output signal OUT to at least the inputterminal of inverter 448 or node n5.

Inverter 448 is coupled between node n5 and node n6. Inverter 448 isconfigured to generate an inverted output signal OUTB (e.g., feedbacksignal FS1) in response to output signal OUT (e.g., the feedback signalFS2). In some embodiments, the inverted output signal OUTB correspondsto feedback signal FS1. An input terminal of inverter 448 is coupled toat least the output terminal of inverter 442 or node n5. The inputterminal of inverter 448 is configured to receive the output signal OUTfrom at least node n5. An output terminal of inverter 448 is coupled toat least node n6 or an input terminal of inverter 450. The outputterminal of inverter 448 is configured to output the inverted outputsignal OUTB to at least node n6 or the input terminal of inverter 450.

Inverter 450 is coupled between node n6 and an output node of circuit400. Inverter 450 is configured to generate output signal OUT inresponse to the inverted output signal OUTB. The input terminal ofinverter 450 is coupled to at least node n6 or the output terminal ofinverter 448. The input terminal of inverter 450 is configured toreceive the inverted output signal OUTB from inverter 448. An outputterminal of inverter 450 is coupled to the output node of circuit 400.The output terminal of inverter 450 is configured to output the outputsignal OUT to the output node of circuit 400.

In comparison with feedback circuit 220 of FIG. 2, the gate terminal ofPMOS transistor m9 of feedback circuit 420 and the gate terminal of NMOStransistor m15 of feedback circuit 420 are coupled to at least node n6.Feedback signal FS1 corresponds to the signal at node n6.

Node n6 of output circuit 440 is coupled to at least the output terminalof inverter 448, the input terminal of inverter 450, the gate terminalof PMOS transistor m9 or the gate terminal of NMOS transistor m15.Inverter 448 of output circuit 440 is configured to generate feedbacksignal FS1 in response to feedback signal FS2 or output signal OUT.Thus, inverter 448 is configured to control feedback circuit 420 byfeedback signal FS1.

In comparison with feedback circuit 230 of FIG. 2, the gate terminal ofPMOS transistor m10 of feedback circuit 430 and the gate terminal ofNMOS transistor m16 of feedback circuit 430 are coupled to node n5.Feedback signal FS2 corresponds to the signal at node n5.

Node n5 of output circuit 440 is coupled to at least the input terminalof inverter 448, the output terminal of inverter 442, the gate terminalof PMOS transistor m10 or the gate terminal of NMOS transistor m16.Inverter 442 of output circuit 440 is configured to generate feedbacksignal FS2 (or inverted output signal OUTB) in response to first signalSH1. Thus, inverter 442 is configured to control feedback circuit 430 byfeedback signal FS2.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 410, and by including NMOS transistor m6 in thesecond path of level shifter circuit 410, short circuit currents in thefirst path and the second path of level shifter circuit 410 areprevented when level shifter circuit 410 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 440 such thatfeedback circuit 420 is coupled to node n6 or feedback circuit 430 iscoupled to node n5, circuit 400 includes less circuit elements thanother approaches resulting in less power consumption and less area thanother approaches. In some embodiments, by using circuit 400, feedbackcircuit 420 and feedback circuit 430 are configured to assist withlatching of the output data signal OUT, and therefore circuit 400includes less circuit elements than other approaches resulting in lesslower power consumption and less area than other approaches.

FIG. 5 is a circuit diagram of a circuit 500, in accordance with someembodiments. Circuit 500 is an embodiment of integrated circuit 100B ofFIG. 1B and similar detailed description is therefore omitted.

Circuit 500 includes enable circuit 204, input circuit 402, a levelshifter circuit 510, a feedback circuit 520, a feedback circuit 530 andan output circuit 540. Level shifter circuit 510 is an embodiment oflevel shifter circuit 110′ of FIG. 1B, and similar detailed descriptionis omitted. Feedback circuits 520 and 530 are embodiments ofcorresponding feedback circuits 120′ and 130′ of FIG. 1B, and similardetailed description is omitted. Output circuit 540 is an embodiment ofoutput circuit 140′ of FIG. 1B, and similar detailed description isomitted.

Circuit 500 is a variation of circuit 400 of FIG. 4, and similardetailed description is therefore omitted. In comparison with circuit400 of FIG. 4, the set of feedback signals FS (FS1, FS2) are generatedby a level shifter circuit 510. Thus, first signal SH1 of FIG. 5corresponds to feedback signal FS1, and second signal SH2 of FIG. 1Bcorresponds to feedback signal FS2.

In comparison with circuit 400 of FIG. 4, level shifter circuit 510replaces level shifter circuit 410, feedback circuit 520 replacesfeedback circuit 420, feedback circuit 530 replaces feedback circuit 430and output circuit 540 replaces output circuit 440, and similar detaileddescription is therefore omitted.

In comparison with FIGS. 2-4 and 8, output circuit 540 of FIG. 5 orFIGS. 6-7 and 9 (described below) do not latch the output signal OUT. Insome embodiments, feedback circuits 520 and 530 are configured to latchor maintain a previous state of the output signal OUT in response to atleast feedback signal FS1 (first signal SH1), feedback signal FS2(second signal SH2), enable signal EN, inverted enable signal ENB, inputsignal INB or input signal INBB.

In comparison with output circuit 440 of FIG. 4, output circuit 540 doesnot include inverter 448, inverter 450, node n5, and node n6. The outputterminal of inverter 442 of output circuit 540 is coupled to the outputnode of circuit 500. In comparison with output circuit 440 of FIG. 4,feedback signal FS1 and feedback signal FS2 of circuit 500 are notgenerated by output circuit 540.

In comparison with level shifter circuit 410 and feedback circuit 420 ofFIG. 4, each of the gate terminal of PMOS transistor m9 of feedbackcircuit 520, the gate terminal of NMOS transistor m15 of feedbackcircuit 520, the gate terminal of PMOS transistor m1 of level shiftercircuit 510 and node n4 are coupled to each other. Feedback signal FS1corresponds to first signal SH1 at node n4. In some embodiments,feedback signal FS1 of circuit 500 is generated by level shifter circuit510 or feedback circuit 530. In these embodiments, level shifter circuit510 or feedback circuit 530 is configured to control feedback circuit520 by feedback signal FS1.

In comparison with level shifter circuit 410 and feedback circuit 430 ofFIG. 4, each of the gate terminal of PMOS transistor m10 of feedbackcircuit 530, the gate terminal of NMOS transistor m16 of feedbackcircuit 530, the gate terminal of PMOS transistor m2 of level shiftercircuit 510 and node n3 are coupled to each other. Feedback signal FS2corresponds to second signal SH2 at node n3. In some embodiments,feedback signal FS2 of circuit 500 is generated by level shifter circuit510 or feedback circuit 520. In these embodiments, level shifter circuit510 or feedback circuit 520 is configured to control feedback circuit530 by feedback signal FS2.

In some embodiments, feedback circuit 520 and feedback circuit 530 areconfigured to latch or maintain a previous state of the output signalOUT in response to at least feedback signal FS1 (first signal SH1),feedback signal FS2 (second signal SH2), enable signal EN, invertedenable signal ENB, input signal INB or input signal INBB. In someembodiments, level shifter circuit 510 is configured to assist feedbackcircuit 520 and feedback circuit 530 to latch or maintain a previousstate high state (e.g., VDDO) of the output signal OUT.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 510, and by including NMOS transistor m6 in thesecond path of level shifter circuit 510, short circuit currents in thefirst path and the second path of level shifter circuit 510 areprevented when level shifter circuit 510 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 540 in circuit500, circuit 500 includes less circuit elements than other approachesresulting in less lower power consumption and less area than otherapproaches. In some embodiments, by using circuit 500, feedback circuit520 and feedback circuit 530 are configured to latch the output signalOUT, and therefore circuit 500 includes less circuit elements than otherapproaches resulting in less lower power consumption and less area thanother approaches. In some embodiments, by using circuit 500, levelshifter circuit 510, feedback circuit 520 and feedback circuit 530 areconfigured to generate feedback signal FS1 and feedback signal FS2, andare configured to latch the output signal OUT, and therefore circuit 500includes less circuit elements than other approaches resulting in lesslower power consumption than other approaches.

FIG. 6 is a circuit diagram of a circuit 600, in accordance with someembodiments. Circuit 600 is an embodiment of integrated circuit 100B ofFIG. 1B and similar detailed description is therefore omitted.

Circuit 600 is a variation of circuit 500 of FIG. 5, and similardetailed description is therefore omitted. In comparison with circuit500 of FIG. 5, at least feedback circuit 620 or 630 does not include apull-up transistor device configured to latch the high state (e.g.,VDDO) of either the first node n3 or the second node n4. In other words,at least one of the pull-up transistor devices of level shifter circuit610 is configured to latch the high state (e.g., VDDO) of either thefirst node n3 or the second node n4.

In comparison with circuit 500 of FIG. 5, level shifter circuit 610replaces level shifter circuit 510, feedback circuit 620 replacesfeedback circuit 520, feedback circuit 630 replaces feedback circuit530, and similar detailed description is therefore omitted.

In comparison with level shifter circuit 510 of FIG. 5, level shiftercircuit 610 does not include PMOS transistor m3 and PMOS transistor m4.In some embodiments, the drain of PMOS transistor m1 is directly coupledto the first node n3. In some embodiments, the drain of PMOS transistorm2 is directly coupled to the second node n4.

In comparison with feedback circuit 520 of FIG. 5, feedback circuit 620does not include PMOS transistor m9 and PMOS transistor m11. In otherwords, feedback circuit 620 does not include pull-up transistors to pullthe first node n3 towards supply voltage VDDO. By not including PMOStransistor m9 and PMOS transistor m11, feedback circuit 620 is notconfigured to pull the first node n3 towards supply voltage VDDO, andPMOS transistor m1 of the level shifter circuit 610, if turned on, isconfigured to pull the first node n3 towards supply voltage VDDO.

In comparison with feedback circuit 520 of FIG. 5, feedback circuit 630does not include PMOS transistor m10 and PMOS transistor m12. In otherwords, feedback circuit 630 does not include pull-up transistors to pullthe second node n4 towards supply voltage VDDO. By not including PMOStransistor m10 and PMOS transistor m12, feedback circuit 630 is notconfigured to pull the second node n4 towards supply voltage VDDO, andPMOS transistor m2 of the level shifter circuit 610, if turned on, isconfigured to pull the second node n4 towards supply voltage VDDO. Insome embodiments, level shifter circuit 610 is configured to latch ormaintain a previous state high state (e.g., VDDO) of the output signalOUT.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 610, and by including NMOS transistor m6 in thesecond path of level shifter circuit 610, short circuit currents in thefirst path and the second path of level shifter circuit 610 areprevented when level shifter circuit 610 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 540 in circuit600, circuit 600 includes less circuit elements than other approachesresulting in less lower power consumption than other approaches.

In some embodiments, by using circuit 600, feedback circuit 620 andfeedback circuit 630 are configured to latch the output signal OUT, andtherefore circuit 600 includes less circuit elements than otherapproaches resulting in less lower power consumption and less area thanother approaches. In some embodiments, by using circuit 600, levelshifter circuit 510, feedback circuit 620 and feedback circuit 630 areconfigured to generate feedback signal FS1 and feedback signal FS2, andare configured to latch the output signal OUT, and therefore circuit 600includes less circuit elements than other approaches resulting in lesslower power consumption than other approaches.

In some embodiments, by using circuit 600, level shifter circuit 610,feedback circuit 620 and feedback circuit 630 are configured to latchthe output data signal OUT, and therefore circuit 600 includes lesscircuit elements than other approaches resulting in less lower powerconsumption and less area than other approaches. In some embodiments, byusing circuit 600, level shifter circuit 610, feedback circuit 620 andfeedback circuit 630 are configured to generate feedback signal FS1 andfeedback signal FS2, and therefore circuit 600 includes less circuitelements than other approaches resulting in less lower power consumptionand less area than other approaches.

FIG. 7 is a circuit diagram of a circuit 700, in accordance with someembodiments. Circuit 700 is an embodiment of integrated circuit 100B ofFIG. 1B and similar detailed description is therefore omitted.

Circuit 700 is a variation of circuit 500 of FIG. 5, and similardetailed description is therefore omitted. In comparison with circuit500 of FIG. 5, a number of transistors in at least feedback circuit 720or 730 is reduced.

In comparison with circuit 500 of FIG. 5, feedback circuit 720 replacesfeedback circuit 520, feedback circuit 730 replaces feedback circuit530, and similar detailed description is therefore omitted.

In comparison with feedback circuit 520 of FIG. 5, feedback circuit 720does not include at least NMOS transistor m13. In other words, feedbackcircuit 720 includes at least one less pull-down transistor in the firstpath of feedback circuit 720. In some embodiments, by not including atleast NMOS transistor m13, control of feedback circuit 720 issimplified. In some embodiments, by not including at least NMOStransistor m13, less connections between enable circuit 204 andtransistors within the feedback circuit 720 are utilized, and thecomplexity of the signal routing is reduced. In some embodiments, thedrain of NMOS transistor m15 of feedback circuit 720 is directly coupledto at least the first node n3. Other configurations, number oftransistors or transistor types of feedback circuit 720 are within thescope of the present disclosure.

In comparison with feedback circuit 530 of FIG. 5, feedback circuit 730does not include at least NMOS transistor m13. In other words, feedbackcircuit 730 includes at least one less pull-down transistor in the firstpath of feedback circuit 730. In some embodiments, by not including atleast NMOS transistor m14, control of feedback circuit 730 issimplified. In some embodiments, by not including at least NMOStransistor m14, less connections between enable circuit 204 andtransistors within the feedback circuit 730 are utilized, and thecomplexity of the signal routing is reduced. In some embodiments, thedrain of NMOS transistor m16 of feedback circuit 730 is directly coupledto at least the second node n4. Other configurations, number oftransistors or transistor types of feedback circuit 730 are within thescope of the present disclosure.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 710, and by including NMOS transistor m6 in thesecond path of level shifter circuit 710, short circuit currents in thefirst path and the second path of level shifter circuit 710 areprevented when level shifter circuit 710 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 540 in circuit700, circuit 700 includes less circuit elements than other approachesresulting in less lower power consumption than other approaches. In someembodiments, by using circuit 700, level shifter circuit 510, feedbackcircuit 720 and feedback circuit 730 are configured to latch the outputdata signal OUT, and therefore circuit 700 includes less circuitelements than other approaches resulting in less lower power consumptionand less area than other approaches. In some embodiments, by usingcircuit 700, level shifter circuit 610, feedback circuit 720 andfeedback circuit 730 are configured to generate feedback signal FS1 andfeedback signal FS2, and therefore circuit 700 includes less circuitelements than other approaches resulting in less lower power consumptionand less area than other approaches.

In some embodiments, by not including at least NMOS transistor m13 orm14, control of feedback circuit 720 or 730 is simplified. In someembodiments, by not including at least NMOS transistor m13 or m14, lessconnections between enable circuit 204 and transistor m13 or m14 withincorresponding feedback circuit 720 or 730 are utilized, and thereforethe complexity of signal routing in circuit 700 is reduced, andtherefore circuit 700 includes less circuit elements than otherapproaches resulting in less lower power consumption and less area thanother approaches.

FIG. 8 is a circuit diagram of a circuit 800, in accordance with someembodiments. Circuit 800 is an embodiment of integrated circuit 100A ofFIG. 1A and similar detailed description is therefore omitted.

Circuit 800 is a variation of circuit 400 of FIG. 4, and similardetailed description is therefore omitted. In comparison with circuit400 of FIG. 4, level shifter circuit 810 replaces level shifter circuit410, and level shifter circuit 810 has a wider range of operatingvoltages than level shifter circuit 410.

In comparison with circuit 400 of FIG. 4, level shifter circuit 810replaces level shifter circuit 410, feedback circuit 820 replacesfeedback circuit 420, feedback circuit 830 replaces feedback circuit430, output circuit 840 replaces output circuit 440, and similardetailed description is therefore omitted.

In comparison with output circuit 440 of FIG. 4, nodes n6 and n7 ofoutput circuit 840 replace corresponding nodes n5 and n6, and similardetailed description is therefore omitted. Feedback signal FS2 ofcircuit 800 corresponds to the signal at node n6, and feedback signalFS1 of circuit 800 corresponds to the signal at node n7.

In comparison with level shifter circuit 410 of FIG. 4, level shiftercircuit 810 includes a level shifter circuit 810 a and a level shiftercircuit 810 b. Node n5 of level shifter circuit 810 b corresponds to theoutput node of level shifter 810.

Level shifter circuit 810 a is a variation of level shifter circuit 410of FIG. 4, and similar detailed description is therefore omitted. Incomparison with level shifter circuit 410 of FIG. 4, PMOS transistor m3of level shifter circuit 810 a is in a diode-coupled configuration, andPMOS transistor m4 of level shifter circuit 810 a is in a diode-coupledconfiguration. Thus, the gate terminal of PMOS transistor m3 of levelshifter circuit 810 a is coupled to at least the drain terminal of PMOStransistor m3 at first node n3. Similarly, the gate terminal of PMOStransistor m4 of level shifter circuit 810 a is coupled to at least thedrain terminal of PMOS transistor m4 at second node n4.

In level shifter circuit 810 a, each of the gate terminal of PMOStransistor m3, the drain terminal of PMOS transistor m3, the gateterminal of PMOS transistor m2, the drain terminal of PMOS transistorm11, the drain terminal of NMOS transistor m13, the drain terminal ofNMOS transistor m5 and the first node n3 are coupled to each other.

Level shifter circuit 810 b is coupled between the second node n4, noden2 and node n5. Level shifter circuit 810 b is configured to receiveinput signal IN. Level shifter circuit 810 b is configured to output thevoltage of second node n4 or the voltage of node n2 to node n5. Levelshifter circuit 810 b is configured to output or pass the voltage ofsecond node n4 or the voltage of node n2 to the output circuit 840 inresponse to input signal IN.

Level shifter circuit 810 b comprises an NMOS transistor m33 and a PMOStransistor m32.

A gate terminal of PMOS transistor m32 is coupled to at least node n20and configured to receive input signal IN. PMOS transistor m32 is turnedon or off based on input signal IN. Each of a source terminal of PMOStransistor m32, the drain terminal of PMOS transistor m2, the sourceterminal of PMOS transistor m4 and node n2 are coupled to each other.The source terminal of PMOS transistor m32 is configured to receive thevoltage of node n2. In some embodiments, the voltage of node n2 is equalto the supply reference voltage VSS, the supply voltage VDDO or avoltage equal to supply reference voltage VSS +Vth of PMOS transistorm4, where Vth is the threshold voltage of PMOS transistor m4.

A gate terminal of NMOS transistor m33 is coupled to at least node n20and configured to receive input signal IN. NMOS transistor m33 is turnedon or off based on input signal IN. A source terminal of NMOS transistorm33 is coupled with at least the second node n4. A drain terminal ofNMOS transistor m33, and a drain terminal of PMOS transistor m32 are atleast coupled to each other. The source terminal of NMOS transistor m33is configured to receive the voltage of second node n4. In someembodiments, the voltage of second node n4 is equal to the supplyreference voltage VSS, the supply voltage VDDO or a voltage equal tosupply voltage VDDO−Vth of PMOS transistor m4, where Vth is thethreshold voltage of PMOS transistor m4.

Each of the source terminal of NMOS transistor m33, a drain terminal ofNMOS transistor m30 (part of feedback circuit 830 b described below),the gate terminal of PMOS transistor m4, the drain terminal of PMOStransistor m4, the gate terminal of PMOS transistor ml, and the secondnode n4 are coupled to each other.

Each of the drain terminal of NMOS transistor m33, the drain terminal ofPMOS transistor m32, the drain terminal of NMOS transistor m14, thedrain terminal of PMOS transistor m12, the input terminal of inverter442 and the node n5 are coupled to each other.

PMOS transistor m32 and NMOS transistor m33 are configured to operate ina complementary manner For example, in some embodiments, if PMOStransistor m32 is enabled or turned on, then NMOS transistor m33 isdisabled or turned off, and vice versa. NMOS transistor m33 or PMOStransistor m32 is configured to pass at least the voltage of second noden4 or the voltage of node n2 to node n5 as the first signal SH1.

In comparison with feedback circuit 420 of FIG. 4, the gate terminal ofPMOS transistor m9 of feedback circuit 820 and the gate terminal of NMOStransistor m15 of feedback circuit 820 are coupled to at least node n7.Feedback signal FS1 corresponds to the signal at node n7.

Node n7 of output circuit 840 is coupled to at least the output terminalof inverter 448, the input terminal of inverter 450, the gate terminalof PMOS transistor m9 or the gate terminal of NMOS transistor m15.Inverter 448 of output circuit 840 is configured to generate feedbacksignal FS1 in response to feedback signal FS2 or output signal OUT.Thus, inverter 448 is configured to control feedback circuit 820 byfeedback signal FS1.

In comparison with feedback circuit 430 of FIG. 4, feedback circuit 830includes a feedback circuit 830 a and a feedback circuit 830 b. Feedbackcircuit 830 a is a variation of feedback circuit 430 of FIG. 4, andsimilar detailed description is therefore omitted.

In comparison with feedback circuit 430 of FIG. 4, the gate terminal ofPMOS transistor m10 of feedback circuit 830 a and the gate terminal ofNMOS transistor m16 of feedback circuit 830 a are coupled to node n6.Feedback signal FS2 corresponds to the signal at node n6.

Node n6 of output circuit 840 is coupled to at least the input terminalof inverter 448, the output terminal of inverter 442, the gate terminalof PMOS transistor m10 or the gate terminal of NMOS transistor m16.Inverter 442 of output circuit 840 is configured to generate feedbacksignal FS2 (or inverted output signal OUTB) in response to first signalSH1. Thus, inverter 442 is configured to control feedback circuit 820 byfeedback signal FS2.

Feedback circuit 830 b comprises an NMOS transistor m30 and an NMOStransistor m31.

A gate terminal of NMOS transistor m30 is coupled to at least the noden32 and configured to receive inverted enable signal ENB. NMOStransistor m30 is turned on or off based on inverted enable signal ENB.The drain terminal of NMOS transistor m30 is coupled to at least thesecond node n4.

A drain terminal of NMOS transistor m31 and a source terminal of NMOStransistor m30 are coupled to each other. A gate terminal of NMOStransistor m31 is coupled to at least node n6 of output circuit 840 andconfigured to receive feedback signal FS2. In some embodiments, each ofthe gate terminal of NMOS transistor m31, the gate terminal of NMOStransistor m16, node n6 of output circuit 840, the gate terminal of PMOStransistor m10, the output terminal of inverter 442, and the inputterminal of inverter 448 are coupled together. NMOS transistor m31 isturned on or off based on feedback signal FS2. A source terminal of NMOStransistor m31 is coupled with at least the reference supply node VSS.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 810, and by including NMOS transistor m6 in thesecond path of level shifter circuit 810, short circuit currents in thefirst path and the second path of level shifter circuit 810 areprevented when level shifter circuit 810 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 840 in circuit800, circuit 800 includes less circuit elements than other approachesresulting in less lower power consumption than other approaches. In someembodiments, by using circuit 800, level shifter circuit 810, feedbackcircuit 820 and feedback circuit 830 are configured to latch the outputsignal OUT, and therefore circuit 800 includes less circuit elementsthan other approaches resulting in less lower power consumption and lessarea than other approaches.

In some embodiments, by using at least diode coupled transistors m3 andm4 in level shifter circuit 810 a, transistors m32 and m33 in levelshifter circuit 810 b or feedback circuit 830, circuit 800 has a widerrange of operating voltages than other approaches, resulting in lowerpower consumption and less area than other approaches.

FIG. 9 is a circuit diagram of a circuit 900, in accordance with someembodiments. Circuit 900 is an embodiment of integrated circuit 100B ofFIG. 1B and similar detailed description is therefore omitted.

Circuit 900 is a variation of circuit 400 of FIG. 4 or circuit 800 ofFIG. 8, and similar detailed description is therefore omitted.

Circuit 900 is a variation of circuit 800 of FIG. 8, and similardetailed description is therefore omitted. In comparison with circuit800 of FIG. 8, level shifter circuit 910 replaces level shifter circuit810, and level shifter circuit 910 is configured to generate feedbacksignals FS1 and FS2. Level shifter circuit 910 is an embodiment of levelshifter circuit 110′ of FIG. 1B, and similar detailed description istherefore omitted.

In comparison with circuit 500 of FIG. 5, level shifter circuit 910 ofFIG. 9 replaces level shifter circuit 510, and therefore level shiftercircuit 910 has a wider range of operating voltages than level shiftercircuit 510.

In comparison with circuit 800 of FIG. 8, level shifter circuit 910replaces level shifter circuit 810, feedback circuit 920 replacesfeedback circuit 820, feedback circuit 930 replaces feedback circuit830, output circuit 540 replaces output circuit 440, and similardetailed description is therefore omitted. Level shifter circuit 910 isan embodiment of level shifter circuit 110′ of FIG. 1B, and similardetailed description is therefore omitted.

In comparison with output circuit 840 of FIG. 8, output circuit 540 ofcircuit 900 does not generate feedback signals FS1 and FS2. Levelshifter circuit 910 is configured to generate feedback signals FS1 andFS2.

In comparison with level shifter circuit 810 of FIG. 8, level shiftercircuit 910 includes a level shifter circuit 910 a, a level shiftercircuit 910 b and a level shifter circuit 910 c.

In comparison with level shifter circuit 810 of FIG. 8, an output node(e.g., node n7) of level shifter circuit 910 is coupled to at leastfeedback circuit 920, and an output node (e.g., node n6) of levelshifter circuit 910 is coupled to at least feedback circuit 930.

Feedback signal FS1 corresponds to the voltage of output node (e.g.,node n7) of level shifter circuit 910. Level shifter circuits 910 a and910 b are configured to output feedback signal FS1 to at least feedbackcircuit 920.

Feedback signal FS2 corresponds to the voltage of output node (e.g.,node n6) of level shifter circuit 910. Level shifter circuits 910 a and910 c are configured to output feedback signal FS2 to at least feedbackcircuit 930.

Level shifter circuit 910 a is a variation of level shifter circuit 810a of FIG. 8, and similar detailed description is therefore omitted.Level shifter circuit 910 a is coupled to node n7 by level shiftercircuit 910 b, and coupled to node n6 by level shifter 910 c.

In comparison with level shifter circuit 810 a of FIG. 8, each of thegate terminal of PMOS transistor m3, the drain terminal of PMOStransistor m3, the gate terminal of PMOS transistor m2, the drainterminal of NMOS transistor m5, a drain terminal of NMOS transistor m36(part of feedback circuit 920 b described below), a source terminal ofNMOS transistor m35 (part of level shifter circuit 910 c describedbelow) and the first node n3 are coupled to each other.

In comparison with level shifter circuit 810 a of FIG. 8, each of thesource terminal of PMOS transistor m3, the drain terminal of PMOStransistor ml, a source terminal of PMOS transistor m34 (part of levelshifter circuit 910 c described below), and node n1 are coupled to eachother.

Level shifter circuit 910 b is a variation of level shifter circuit 810b of FIG. 8, and similar detailed description is therefore omitted.

In comparison with level shifter circuit 810 b of FIG. 8, node n7 oflevel shifter circuit 910 b corresponds to the output node of levelshifter circuit 910. Node n7 of level shifter circuit 910 couples thedrain terminal of NMOS transistor m33 and the drain terminal of PMOStransistor m32 to each other. Node n7 of level shifter circuit 910 bcorresponds to node n5, and vice versa. Feedback signal FS1 correspondsto the voltage of output node (e.g., node n7) of level shifter circuit910. Level shifter circuit 910 b is configured to output feedback signalFS1.

In comparison with level shifter circuit 810 b and feedback circuit 820of FIG. 8, each of the drain terminal of NMOS transistor m33, the drainterminal of PMOS transistor m32, the gate terminal of PMOS transistor m9of feedback circuit 920 a (described below), the gate terminal of NMOStransistor m15 of feedback circuit 920 a (described below), a gateterminal m37 of NMOS transistor of feedback circuit 920 b (describedbelow), the drain of NMOS transistor m14, the drain of PMOS transistorm12, the input terminal of inverter 442 and node n7 (or node n5) arecoupled to each other.

Level shifter circuits 910 a and 910 c are configured to output feedbacksignal FS2 to at least feedback circuit 930. Feedback signal FS2corresponds to the voltage of another output node (e.g., node n6) oflevel shifter circuit 910.

Level shifter circuit 910 c is coupled between the first node n3, noden1 and node n6. Level shifter circuit 910 c is configured to receiveinput signal INB. Level shifter circuit 910 c is configured to outputthe voltage of first node n3 or the voltage of node n1 to node n6 asfeedback signal FS2. Level shifter circuit 910 c is configured to outputor pass the voltage of first node n3 or the voltage of node n1 to theoutput circuit 840 as feedback signal FS2 in response to input signalINB. Level shifter circuit 910 c comprises an NMOS transistor m35 and aPMOS transistor m34.

A gate terminal of PMOS transistor m34 is coupled to at least node n22and configured to receive input signal INB. PMOS transistor m34 isturned on or off based on input signal INB. Each of a source terminal ofPMOS transistor m34, the drain terminal of PMOS transistor ml, thesource terminal of PMOS transistor m3 and node n1 are coupled to eachother. The source terminal of PMOS transistor m34 is configured toreceive the voltage of node nl. In some embodiments, the voltage of noden1 is equal to the supply reference voltage VSS, the supply voltage VDDOor a voltage equal to supply reference voltage VSS +Vth of PMOStransistor m3, where Vth is the threshold voltage of PMOS transistor m3.

A gate terminal of NMOS transistor m35 is coupled to at least node n20and configured to receive input signal INB. NMOS transistor m35 isturned on or off based on input signal INB. A source terminal of NMOStransistor m35 is coupled with at least the first node n3. The sourceterminal of NMOS transistor m35 is configured to receive the voltage offirst node n3. In some embodiments, the voltage of first node n3 isequal to the supply reference voltage VSS, the supply voltage VDDO or avoltage equal to supply voltage VDDO−Vth of PMOS transistor m3, whereVth is the threshold voltage of PMOS transistor m3.

Node n6 of level shifter circuit 910 c corresponds to another outputnode of level shifter circuit 910. Node n6 of level shifter circuit 910couples a drain terminal of NMOS transistor m35 and a drain terminal ofPMOS transistor m34 to each other.

Each of the drain terminal of NMOS transistor m35, the drain terminal ofPMOS transistor m34, the gate terminal of PMOS transistor m11 offeedback circuit 920 a, the gate terminal of NMOS transistor m15 offeedback circuit 920 a, a gate terminal m37 of NMOS transistor offeedback circuit 920 b (described below) and node n6 are coupled to eachother.

PMOS transistor m34 and NMOS transistor m35 are configured to operate ina complementary manner For example, in some embodiments, if PMOStransistor m34 is enabled or turned on, then NMOS transistor m35 isdisabled or turned off, and vice versa. NMOS transistor m35 or PMOStransistor m34 is configured to pass at least the voltage of first noden3 or the voltage of node n1 to node n6 as the feedback signal FS2.

In comparison with circuit 800 of FIG. 8, feedback circuit 930 areplaces feedback circuit 830 a, and feedback circuit 930 b replacesfeedback circuit 830 b, and similar detailed description is thereforeomitted.

In comparison with feedback circuits 830 a and 830 b of FIG. 8, feedbacksignal FS2 at node n6 is generated by at least level shifter circuit 910a or 910 c, and not output circuit 840.

Each of feedback circuits 930 a and 930 b are configured to receivefeedback signal FS2. Feedback circuits 930 a and 930 b are controlled byat least level shifter circuit 910 a or 910 c via feedback signal FS2.

Each of the gate terminal of PMOS transistor m10 of feedback circuit 930a, the gate terminal of NMOS transistor m16 of feedback circuit 930 aand the gate terminal of NMOS transistor m31 of feedback circuit 930 bare configured to receive feedback signal FS2 from level shifter circuit910 c.

In comparison with feedback circuit 820 of FIG. 8, the gate terminal ofPMOS transistor m9 of feedback circuit 930 and the gate terminal of NMOStransistor m15 of feedback circuit 930 are coupled to at least node n7.Feedback signal FS1 corresponds to the signal at node n7.

In comparison with feedback circuit 820 of FIG. 8, feedback circuit 920includes a feedback circuit 920 a and a feedback circuit 920 b. Feedbackcircuit 920 a is a variation of feedback circuit 820 of FIG. 8, andsimilar detailed description is therefore omitted.

In comparison with feedback circuit 820 of FIG. 8, feedback signal FS1at node n7 is generated by at least level shifter circuit 910 a or 910b, and not output circuit 840.

Each of feedback circuits 920 a and 920 b are configured to receivefeedback signal FS1. Feedback circuits 920 a and 920 b are controlled byat least level shifter circuit 910 a or 910 b via feedback signal FS1.

Each of the gate terminal of PMOS transistor m9 of feedback circuit 920a, the gate terminal of NMOS transistor m15 of feedback circuit 920 a,the gate terminal of NMOS transistor m37 of feedback circuit 920 b andthe input terminal of inverter 442 of output circuit 540 are configuredto receive feedback signal FS1 from level shifter circuit 910 b. Atleast level shifter circuit 910 a or 910 b is configured to controlfeedback circuit 920 by feedback signal FS1.

Feedback circuit 920 b comprises an NMOS transistor m36 and an NMOStransistor m37.

A gate terminal of NMOS transistor m36 is coupled to at least node n32and configured to receive inverted enable signal ENB. NMOS transistorm36 is turned on or off based on inverted enable signal ENB. The drainterminal of NMOS transistor m36 is coupled to at least the first noden3.

A drain terminal of NMOS transistor m37 and a source terminal of NMOStransistor m36 are coupled to each other. A gate terminal of NMOStransistor m37 is coupled to at least node n7 of level shifter circuit910 b and configured to receive feedback signal FS2. NMOS transistor m37is turned on or off based on feedback signal FS2. A source terminal ofNMOS transistor m37 is coupled with at least the reference supply nodeVSS.

In some embodiments, by including NMOS transistor m5 in the first pathof level shifter circuit 810, and by including NMOS transistor m6 in thesecond path of level shifter circuit 810, short circuit currents in thefirst path and the second path of level shifter circuit 810 areprevented when level shifter circuit 810 is disabled by the enablesignal EN resulting in lower power consumption than other approaches. Insome embodiments, by using a different output circuit 840 in circuit800, circuit 800 includes less circuit elements than other approachesresulting in less lower power consumption than other approaches. In someembodiments, by using circuit 800, level shifter circuit 810, feedbackcircuit 820 and feedback circuit 830 are configured to latch the outputsignal OUT, and therefore circuit 800 includes less circuit elementsthan other approaches resulting in less lower power consumption and lessarea than other approaches.

In some embodiments, by using circuit 900, level shifter circuit 910,feedback circuit 920 and feedback circuit 930 are configured to generatefeedback signal FS1 and feedback signal FS2, and therefore circuit 900includes less circuit elements than other approaches resulting in lesslower power consumption and less area than other approaches.

In some embodiments, by using at least diode coupled transistors m3 andm4 in level shifter circuit 910 a, transistors m32 and m33 in levelshifter circuit 910 b, transistors m34 and m35 in level shifter circuit910 c, feedback circuit 920 or feedback circuit 930, circuit 900 has awider range of operating voltages than other approaches, resulting inlower power consumption and less area than other approaches.

Method

FIGS. 10A-10B are a flowchart of a method of operating a circuit, suchas the circuit of FIGS. 1A-1B or FIGS. 2-8, in accordance with someembodiments. It is understood that additional operations may beperformed before, during, and/or after the method 1000 depicted in FIG.10, and that some other processes may only be briefly described herein.It is understood that method 1000 utilizes features of one or more ofcircuits 100A-100B of FIGS. 1A-1B or circuits 200-800 of correspondingFIGS. 2-8.

In operation 1002 of method 1000, a first enable signal (enable signalEN), a second enable signal (inverted enable signal ENB) or an inputsignal (IN, INB or INBB) is received by a level shifter circuit 110 or110′.

In operation 1004 of method 1000, level shifter circuit 110 or 110′ isturned on or enabled in response to enable signal EN, or a feedbackcircuit 220 or 230 is turned off or disabled in response to at leastenable signal EN. In some embodiments, level shifter circuit 110 or 110′is turned on or enabled in response to enable signal EN having a firstlogical value, or feedback circuit 220 or 230 is turned off or disabledin response to enable signal EN having the first logical value. In someembodiments, the first logical value is a logical high. In someembodiments the first logical value is a logical low.

In some embodiments, level shifter circuit 110 or 110′ and feedbackcircuit 220 or 230 are operated in a complementary manner such thatturning on one of level shifter circuit 110 or 110′ or feedback circuit220 or 230 turns off the other of the level shifter circuit 110 or 110′or feedback circuit 220 or 230, and vice versa. In some embodiments,turning on or enabling level shifter circuit 110 or 110′ comprisesturning off or disabling the feedback circuit 220 or 230. In someembodiments, turning off or disabling the feedback circuit 220 or 230comprises turning on or enabling level shifter circuit 110 or 110′. Insome embodiments, operation 1004 comprises one or more of operations1006, 1008 or 1010. In some embodiments, operations 1006, 1008 and 1010occur in response to enable signal EN having the first logical value. Insome embodiments, operation 1004 of method 1000 further comprisesturning on or switching on a first voltage supply (voltage supply VDDI).In some embodiments, the first voltage supply has the first voltageswing. In some embodiments, turning on or switching on the first voltagesupply (voltage supply VDDI) comprises turning on a transistor (PMOStransistor m0) responsive to a power enable signal Pin, such that PMOStransistor m0 provides supply voltage VDDI to at least a first voltagesupply node IN, an inverter 202 a or inverter 402 a.

In operation 1006 of method 1000, at least a first input path or asecond input path in level shifter circuit 110 or 110′ is enabled inresponse to at least enable signal EN or inverted enable signal ENB. Insome embodiments, the first input path of level shifter circuit 210includes one or more of NMOS transistor m5, NMOS transistor m7, PMOStransistor m1 or PMOS transistor m3. In some embodiments the secondinput path of level shifter 210 includes one or more of NMOS transistorm6, NMOS transistor M8, PMOS transistor m2 or PMOS transistor m4 arereferred to as a second input path of level shifter circuit 210.

In operation 1008 of method 1000, at least a first feedback path or asecond feedback path in feedback circuit 220 or 230 is disabled inresponse to at least the first enable signal EN (enable signal EN), thesecond enable signal(inverted enable signal ENB) or the set of feedbacksignals FS. In some embodiments, the first feedback path of feedbackcircuit 220 includes one or more of NMOS transistor m13, NMOS transistorm15, PMOS transistor m9 or PMOS transistor m11. In some embodiments, thesecond feedback path of feedback circuit 230 includes one or more ofNMOS transistor m14, NMOS transistor m16, PMOS transistor m10 or PMOStransistor m12.

In operation 1010 of method 1000, level shifter circuit 110 or 110′generates at least a first signal SH1 or a second signal SH2 in responseto at least the first enable signal (enable signal EN) and an inputsignal IN, INB or INBB. In some embodiments, input signal IN, INB orINBB has the first voltage swing. In some embodiments, the first signalSH1 or the second signal SH2 has the second voltage swing different fromthe first voltage swing. In some embodiments, the first signal SH1 isinverted from input signal IN or INBB. In some embodiments, the secondsignal SH2 is inverted from input signal INB.

In operation 1012 of method 1000, level shifter circuit 110 or 110′ isturned off or disabled in response to the first enable signal (enablesignal EN), or feedback circuit 220 or 230 is turned on or enabled inresponse to at least the first enable signal (enable signal EN).

In some embodiments, level shifter circuit 110 or 110′ is turned off ordisabled in response to enable signal EN having the second logicalvalue, or feedback circuit 220 or 230 is turned on or enabled inresponse to enable signal EN having the second logical value. The secondlogical value is inverted from the first logical value. In someembodiments, the second logical value is a logical low. In someembodiments the second logical value is a logical high. In someembodiments, turning off or disabling level shifter circuit 110 or 110′comprises turning on or enabling the feedback circuit 220 or 230. Insome embodiments, turning on or enabling the feedback circuit 220 or 230comprises turning off or disabling level shifter circuit 110 or 110′. Insome embodiments, operation 1012 comprises one or more of operations1014, 1016, 1018 or 1020. In some embodiments, operations 1014, 1016,1018 and 1020 occur in response to enable signal EN having the secondlogical value and inverted enable signal having the first logical value.

In operation 1014 of method 1000, a first voltage supply (voltage supplyVDDI) is turned off or switched off. In some embodiments, the firstvoltage supply has the first voltage swing. In some embodiments,operation 1014 comprises turning off a transistor (PMOS transistor m0)responsive to a power enable signal Pin, such that PMOS transistor m0does not provide supply voltage VDDI to at least a first voltage supplynode IN, an inverter 202 a or inverter 402 a.

In operation 1016 of method 1000, at least a first input path or asecond input path in level shifter circuit 110 or 110′ is disabled inresponse to at least enable signal EN or inverted enable signal ENB.

In operation 1018 of method 1000, at least a first feedback path or asecond feedback path in feedback circuit 220 or 230 is enabled inresponse to at least the first enable signal EN (enable signal EN), thesecond enable signal (inverted enable signal ENB) or the set of feedbacksignals FS.

In operation 1020 of method 1000, a latched output signal (e.g., OUT) isgenerated. In some embodiments, operation 1020 includes at leastoperation 1020 a or 1020 b. In some embodiments, operations 1020, 1020 aand 1020 b occur in response to enable signal EN having the secondlogical value and inverted enable signal having the first logical value.

In operation 1020 a of method 1000, an output circuit 140 of FIG. 1A isconfigured to latch a previous state of an output signal OUT. In someembodiments, the latched output signal of operation 1020 corresponds tothe previous state of the output signal OUT. In some embodiments,operation 1020 a is performed by inverter 242, inverter 246 andtransmission gate 252 of output circuit 240.

In operation 1020 b of method 1000, feedback circuit 120′ and 130′ ofFIG. 1B are configured to latch the first signal SH1 or the secondsignal SH2. In some embodiments, the latched output signal of operation1020 corresponds to the first signal SH1 or the second signal SH2. Insome embodiments, operation 1020 b is performed by feedback circuit 520and feedback circuit 530.

In some embodiments, a portion of operation 1020 a and a portion ofoperation 1020 b are combined such that portions of output circuit 440or 840 and feedback circuit 420, 430, 820 or 830 are together configuredto latch the output signal OUT (second signal SH2) or inverted outputsignal OUTB (first signal SH1).

In operation 1022 of method 1000, the set of feedback signals FS aregenerated by output circuit 140 or level shifter circuit 110′. In someembodiments, operation 1022 includes generating the set of feedbacksignals FS by output circuit 140 or level shifter circuit 110′. In someembodiments, operation 1022 includes at least operation 1022 a or 1022b.

In some embodiments, operation 1022 a comprises the output circuit 140,240, 340, 440 or 840 being configured to generate the set of feedbacksignals FS. In some embodiments, the set of feedback signals FS includesat least the output signal (OUT) or an inverted output signal (OUTB).

In some embodiments, operation 1022 a is performed in combination withoperation 1020 a. For example, in some embodiments, output circuit 240is configured to latch the output signal OUT and also generate the setof feedback signals FS.

In some embodiments, operation 1022 b comprises the level shiftercircuit 110′, 510, 610 or 910 being configured to generate the set offeedback signals FS.

In some embodiments, operation 1022 b is performed in combination withoperation 1020 b. For example, in some embodiments, at least feedbackcircuit 520, 530, 620, 630, 720, 730, 920 or 930 being configured tolatch the output signal OUT, and level shifter circuits 110′, 510, 610or 910 configured to generate the set of feedback signals FS.

In some embodiments, operation 1022 b is performed in combination withoperation 1020 a. For example, in some embodiments, at least feedbackcircuit 520, 530, 620, 630, 720, 730, 920 or 930 being configured tolatch the first signal SH1 or second signal SH2, and level shiftercircuits 110′, 510, 610 or 910 configured to generate the set offeedback signals FS.

In operation 1024 of method 1000, the output circuit 140 or 140′ isconfigured to output the output signal OUT in response to at least theenable signal EN or the first signal SH1.

In some embodiments, the output signal OUT corresponds to the latchedoutput signal of a previous state of the output signal OUT or aninverted version of the first signal SH1 of circuit 200. In someembodiments, the inverted version of first signal SH1 (e.g., secondsignal SH2) corresponds to a level shifted version of input signal IN.In some embodiments, operation 1024 occurs in response to enable signalEN having the second logical value and inverted enable signal having thefirst logical value.

In some embodiments, the output signal OUT corresponds to the latchedoutput signal of a previous state of the output signal OUT in responseto enable signal EN having the second logical value. In someembodiments, the output signal OUT corresponds to the level shiftedversion of the input signal IN (e.g., inverted version of first signalSH1) in response to enable signal EN having the first logical value.

In some embodiments, one or more of the operations of method 1000 is notperformed. While method 1000 was described above with reference to FIGS.1A-1B & 2, it is understood that method 1000 utilizes the features ofone or more of FIGS. 3-9. In some these embodiments, other operations ofmethod 1000 would be performed consistent with the description andoperation of circuits 300-900 of FIGS. 3-9. Furthermore, various PMOS orNMOS transistors shown in FIGS. 2-9 are of a particular dopant type(e.g., N-type or P-type) are for illustration purposes. Embodiments ofthe disclosure are not limited to a particular transistor type, and oneor more of the PMOS or NMOS transistors shown in FIGS. 2-9 can besubstituted with a corresponding transistor of a differenttransistor/dopant type. Similarly, the low or high logical value ofvarious signals used in the above description is also for illustration.Embodiments of the disclosure are not limited to a particular logicalvalue when a signal is activated and/or deactivated. Selecting differentlogical values is within the scope of various embodiments. Selectingdifferent numbers of inverters in input circuit 202 or 402 is within thescope of various embodiments. Selecting different numbers of invertersin enable circuit 204 is within the scope of various embodiments.Selecting different numbers of inverters in output circuit 240, 340,440, 540 or 840 is within the scope of various embodiments. Selectingdifferent numbers of transmission gates in output circuit 240 or 340 iswithin the scope of various embodiments. Selecting different numbers oftransistors in circuit 200, 300, 400, 500, 600, 700, 800 or 900 iswithin the scope of various embodiments.

One aspect of this description relates to a circuit. In someembodiments, the circuit includes a level shifter circuit, an outputcircuit and a feedback circuit. The level shifter circuit is coupled toa first voltage supply, and is configured to receive at least an enablesignal, a first input signal or a second input signal. The level shiftercircuit is configured to generate at least a first signal responsive toat least the enable signal or the first input signal. The output circuitis coupled to at least the level shifter circuit and the first voltagesupply, is configured to receive the first signal, and to generate atleast an output signal or a set of feedback signals responsive to thefirst signal. The feedback circuit is coupled to the level shiftercircuit, the output circuit and the first voltage supply, and isconfigured to receive the enable signal, an inverted enable signal andthe set of feedback signals.

Another aspect of this description relates to a circuit. In someembodiments, the circuit includes an input circuit, a level shiftercircuit, an output circuit and a feedback circuit. The input circuit iscoupled to a first voltage supply, and is configured to generate atleast a first input signal responsive to a second input signal, thefirst input signal having a first voltage swing. The level shiftercircuit is configured to receive an enable signal and the first inputsignal, and to generate a first signal and a second signal responsive toat least the enable signal or the first input signal, the first signalor the second signal having a second voltage swing different from thefirst voltage swing. The feedback circuit is coupled to the levelshifter circuit, and is configured to latch a previous state of thefirst signal responsive to at least the first signal or the secondsignal. In some embodiments, the feedback circuit includes a firstcircuit having a first set of transistors configured to receive aninverted enable signal and the second signal. The output circuit iscoupled to the level shifter circuit and the feedback circuit, andconfigured to generate an output signal based on at least the firstsignal.

Yet another aspect of this description relates to a method of operatinga circuit. The method includes enabling a level shifter circuit inresponse to a first enable signal. In some embodiments, enabling thelevel shifter circuit includes disabling a first feedback path in afeedback circuit in response to the first enable signal, a second enablesignal and a set of feedback signals, the second enable signal beinginverted from the first enable signal; enabling at least a first inputpath or a second input path in the level shifter circuit in response toat least the first enable signal; and generating at least a first signalor a second signal. In some embodiments, the method further includesoutputting, by an output circuit, an output signal in response to atleast the first enable signal or the first signal. In some embodiments,the output signal corresponds to an inverted first signal.

A number of embodiments have been described. It will nevertheless beunderstood that various modifications may be made without departing fromthe spirit and scope of the disclosure. For example, various transistorsbeing shown as a particular dopant type (e.g., N-type or P-type MetalOxide Semiconductor (NMOS or PMOS)) are for illustration purposes.Embodiments of the disclosure are not limited to a particular type.Selecting different dopant types for a particular transistor is withinthe scope of various embodiments. The low or high logical value ofvarious signals used in the above description is also for illustration.Various embodiments are not limited to a particular logical value when asignal is activated and/or deactivated. Selecting different logicalvalues is within the scope of various embodiments. In variousembodiments, a transistor functions as a switch. A switching circuitused in place of a transistor is within the scope of variousembodiments. In various embodiments, a source of a transistor can beconfigured as a drain, and a drain can be configured as a source. Assuch, the term source and drain are used interchangeably. Varioussignals are generated by corresponding circuits, but, for simplicity,the circuits are not shown.

Various figures show capacitive circuits using discrete capacitors forillustration. Equivalent circuitry may be used. For example, acapacitive device, circuitry or network (e.g., a combination ofcapacitors, capacitive elements, devices, circuitry, or the like) can beused in place of the discrete capacitor. The above illustrations includeexemplary steps, but the steps are not necessarily performed in theorder shown. Steps may be added, replaced, changed order, and/oreliminated as appropriate, in accordance with the spirit and scope ofdisclosed embodiments.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A circuit comprising: a level shifter circuitcoupled to a first voltage supply, and configured to receive at least anenable signal, a first input signal or a second input signal, and togenerate at least a first signal responsive to at least the enablesignal or the first input signal; an output circuit coupled to at leastthe level shifter circuit and the first voltage supply, and configuredto receive the first signal, and to generate at least an output signalor a set of feedback signals responsive to the first signal; and afeedback circuit coupled to the level shifter circuit, the outputcircuit and the first voltage supply, and configured to receive theenable signal, an inverted enable signal and the set of feedbacksignals.
 2. The circuit of claim 1, wherein the level shifter circuitcomprises: a first set of transistors coupled between a first node andthe first voltage supply; a second set of transistors coupled between asecond node and the first voltage supply, a voltage of the first node orthe second node corresponds to a voltage of the first signal; a thirdset of transistors coupled to a reference supply node, and beingconfigured to receive the second input signal; a fourth set oftransistors coupled to the reference supply node, and being configuredto receive the first input signal; a fifth set of transistors coupledbetween the first node and the third set of transistors, a transistor ofthe fifth set of transistors being configured to receive the enablesignal; and a sixth set of transistors coupled between the second nodeand the fourth set of transistors, a transistor of the sixth set oftransistors being configured to receive the enable signal.
 3. Thecircuit of claim 2, wherein the level shifter circuit further comprises:a first transistor coupled between an input node of the output circuitand either the first node or the second node, and configured to receivethe first input signal; and a second transistor coupled between theinput node of the output circuit and a third node of the level shiftercircuit, and configured to receive the first input signal, the thirdnode of the level shifter circuit being between a first transistor ofthe first set of transistors and a second transistor of the first set oftransistors.
 4. The circuit of claim 1, wherein the feedback circuitcomprises: a first circuit having a first set of transistors configuredto receive the enable signal, the inverted enable signal and a firstfeedback signal, and coupled to the first voltage supply, a referencevoltage supply and a first node of the level shifter circuit; and asecond circuit having a second set of transistors configured to receivethe enable signal, the inverted enable signal and a second feedbacksignal inverted from the first feedback signal, and coupled to the firstvoltage supply, the reference voltage supply and a second node of thelevel shifter circuit.
 5. The circuit of claim 1, further comprising: aninput circuit comprising: a first inverter coupled to a second voltagesupply different from the first voltage supply, and configured togenerate the second input signal responsive to the first input signal,the first input signal being inverted from the second input signal. 6.The circuit of claim 5, wherein the input circuit further comprises: asecond inverter coupled to the second voltage supply and the firstinverter, and configured to generate a third input signal responsive tothe second input signal, the third input signal being inverted from thesecond input signal.
 7. The circuit of claim 1, wherein the outputcircuit comprises: a first inverter having a first terminal coupled to afirst node of the level shifter circuit, and configured to receive thefirst signal, and a second terminal of the first inverter configured tooutput a first feedback signal of the set of feedback signals; a secondinverter having a first terminal coupled to the second terminal of thefirst inverter and configured to receive the first feedback signal ofthe set of feedback signals, and a second terminal of the secondinverter configured to output a second feedback signal of the set offeedback signals; and a third inverter having a first terminal coupledto the second terminal of the second inverter and configured to receivethe second feedback signal of the set of feedback signals, and a secondterminal of the third inverter configured to output the output signal.8. The circuit of claim 1, wherein the output circuit comprises: a setof transistors coupled to the level shifter circuit and the feedbackcircuit, and configured to generate the output signal; a latch circuitcoupled to the set of transistors, and configured to latch a previousstate of the output signal responsive to at least the enable signal; anda first inverter coupled to an output of the latch circuit by a firstnode, and configured to output the output signal.
 9. The circuit ofclaim 8, wherein the set of transistors comprises: a first p-typetransistor having a first terminal coupled to an output node of thelevel shifter circuit and the feedback circuit, and configured toreceive the first signal, and a second terminal of the first p-typetransistor is coupled to the first voltage supply; a second p-typetransistor having a first terminal configured to receive the invertedenable signal, a second terminal of the second p-type transistor iscoupled to a third terminal of the first p-type transistor, and a thirdterminal of the second p-type transistor is coupled to a second node; afirst n-type transistor having a first terminal configured to receivethe enable signal, and a second terminal of the first n-type transistoris coupled to the third terminal of the second p-type transistor by thesecond node; and a second n-type transistor having a first terminalcoupled to the output node of the level shifter circuit, the firstterminal of the first p-type transistor and the feedback circuit, andconfigured to receive the first signal, a second terminal of the secondn-type transistor is coupled to a third terminal of the first n-typetransistor, and a third terminal of the second n-type transistor iscoupled to a reference voltage supply.
 10. The circuit of claim 9,wherein the latch circuit comprises: a second inverter having a firstterminal coupled to the second node and configured to receive the outputsignal, and a second terminal of the second inverter coupled to thefirst node and configured to output an inverted output signal; a thirdinverter having a first terminal coupled to the second terminal of thesecond inverter by the first node and configured to receive the invertedoutput signal, and a second terminal of the third inverter configured tooutput the output signal; and a transmission gate having a firstterminal coupled to the second terminal of the third inverter, a secondterminal of the transmission gate configured to receive the enablesignal, a third terminal of the transmission gate configured to receivethe inverted enable signal, and a fourth terminal of the transmissiongate is coupled to at least the second node and the first terminal ofthe second inverter and configured to output the output signal.
 11. Thecircuit of claim 10, wherein the output circuit further comprises: afourth inverter having a first terminal coupled to the second node andconfigured to receive the output signal, and a second terminal of thefourth inverter coupled to a third node and configured to output a firstfeedback signal of the set of feedback signals to a first portion of thefeedback circuit; and a fifth inverter having a first terminal coupledto the second terminal of the fourth inverter by the third node andconfigured to receive the inverted output signal, and a second terminalof the fifth inverter coupled to a fourth node and configured to outputa second feedback signal of the set of feedback signals to a secondportion of the feedback circuit.
 12. The circuit of claim 10, whereinthe inverted output signal of the first node is fed back to a firstportion of the feedback circuit as a first feedback signal of the set offeedback signals, and the output signal of the second node is fed backto a second portion of the feedback circuit as a second feedback signalof the set of feedback signals.
 13. A circuit comprising: an inputcircuit coupled to a first voltage supply, and configured to generate atleast a first input signal responsive to a second input signal, thefirst input signal having a first voltage swing; a level shifter circuitconfigured to receive an enable signal and the first input signal, andto generate a first signal and a second signal responsive to at leastthe enable signal or the first input signal, the first signal or thesecond signal having a second voltage swing different from the firstvoltage swing; a feedback circuit coupled to the level shifter circuit,and configured to latch a previous state of the first signal responsiveto at least the first signal or the second signal, the feedback circuitcomprising: a first circuit having a first set of transistors configuredto receive an inverted enable signal and the second signal; and anoutput circuit coupled to the level shifter circuit and the feedbackcircuit, and configured to generate an output signal based on at leastthe first signal.
 14. The circuit of claim 13, wherein the outputcircuit comprises: an inverter coupled to a second voltage supplydifferent from the first voltage supply, the inverter including a firstterminal of the inverter coupled to an output of the level shiftercircuit by a first node, and being configured to receive the firstsignal, and a second terminal of the inverter being configured togenerate the output signal responsive to the first signal.
 15. Thecircuit of claim 13, wherein the input circuit comprises: a firstinverter coupled to the first voltage supply, and being configured togenerate the first input signal responsive to the second input signal,the second input signal being inverted from the first input signal; anda second inverter coupled to the first voltage supply and the firstinverter, and being configured to generate a third input signalresponsive to the first input signal, the third input signal beinginverted from the first input signal.
 16. The circuit of claim 13,wherein the level shifter circuit comprises: a first set of transistorscoupled between a first node and a second voltage supply different fromthe first voltage supply; a second set of transistors coupled between asecond node and the first voltage supply, a voltage of the second nodecorresponds to a voltage of the first signal; a third set of transistorscoupled to a reference voltage supply; a fourth set of transistorscoupled to the reference voltage supply; a fifth set of transistorscoupled between the first node and the third set of transistors, atransistor of the fifth set of transistors being configured to receivethe enable signal; and a sixth set of transistors coupled between thesecond node and the fourth set of transistors, a transistor of the sixthset of transistors being configured to receive the enable signal. 17.The circuit of claim 13, wherein the first circuit is coupled to areference voltage supply and a first node of the level shifter circuit;and the feedback circuit further comprises: a second circuit having asecond set of transistors configured to receive the inverted enablesignal and the first signal, and being coupled to the reference voltagesupply and a second node of the level shifter circuit.
 18. The circuitof claim 17, wherein the first circuit further comprises: a third set oftransistors configured to receive the enable signal and the secondsignal, and being coupled to the first node of the level shifter circuitand a second voltage supply different from the first voltage supply; andthe second circuit further comprises: a fourth set of transistorsconfigured to receive the enable signal and the first signal, and beingcoupled to the second node of the level shifter circuit and the secondvoltage supply.
 19. A method of operating a circuit, the methodcomprising: enabling a level shifter circuit in response to a firstenable signal, wherein enabling the level shifter circuit comprises:disabling a first feedback path in a feedback circuit in response to thefirst enable signal, a second enable signal and a set of feedbacksignals, the second enable signal being inverted from the first enablesignal; enabling at least a first input path or a second input path inthe level shifter circuit in response to at least the first enablesignal; and generating at least a first signal or a second signal; andoutputting, by an output circuit, an output signal in response to atleast the first enable signal or the first signal, wherein the outputsignal corresponds to an inverted first signal.
 20. The method of claim19, wherein the enabling the level shifter circuit further comprises:disabling a second feedback path in the feedback circuit in response tothe first enable signal, the second enable signal and the set offeedback signals; and the generating at least the first signal or thesecond signal comprises: generating at least the first signal or thesecond signal in response to the first enable signal, a first inputsignal and a second input signal, the first input signal and the secondinput signal having a first voltage swing, the first signal or thesecond signal having a second voltage swing different from the firstvoltage swing, and the first input signal being inverted from the secondinput signal.